Metapod's JP crash course P1

OK listen up kiddos, Metapod is gonna learn you some Japanese.

Before starting this I'm going to assume two things. The first is that you already know the basics of how to pronounce Japanese sounds, and the second is that you already know how to read Romanized Japanese. And by that I mean the way Japanese people do it, not this Hepburn bullshit. If you are used to "shi" and "tsu" and crap, LEARN THE WAY JAPANESE PEOPLE DO IT. It will make so many grammar things make SO MUCH MORE SENSE and a lot easier to explain. I'm not going to go into the whole rant here, but basically Hepburn and similar romanization systems are for people who don't know anything about Japanese to help them hopefully guess how to pronounce things, based on the way things sound and not the actual structure of the language. Like imagine how stupid it would be if we tried to teach English to people by spelling tree like "chree" because people pronounce it that way. Stupid as fuck and you would learn worse with crap like that.

OKAY LET'S GO!!!

We're gonna start off learning the three basic types of Japanese sentences. As you probably know, Japanese sentences can be as short as a single word. You can learn other words on your own easily; it's most important to just know which of these three types they are.

Everything here is going to be in 'desu-masu' form (polite language), which is different from how things appear in dictionaries. It's easier to get a foundation with than "plain" forms plus it's more culturally appropriate to use in any situation you'd be speaking Japanese most likely.

～ます　タイプ
~masu type

The first type of sentence is words that can end in ~masu and ~masita and other things. You'll hear these things called "verbs" but they easily cannot line up with verbs in English (example: tigaimasu means wrong/different, which is an adjective in English), so just think of them as masu/masita words.

The word we're going to learn as an example here is 分かります wakarimasu. It means to understand. When used as a single sentence, it means "I understand," "he understands," "she understands," "it understands," "understanding happens" lol. Anything like that. What exactly is doing the understanding is up to context. Basically some kind of understanding is going on.

～いです　タイプ
~i desu type

The second type of sentence/word ends in ~i desu, ~katta desu, and other things. Let's think of an example. We'll go with 美味しいです oisii desu. It means tasty/delicious/whatever Note that it has to end with いです i desu, as the い i part is what gets changed. Simply things that have the letter 'i' at the end of their romanization don't cut it.

So as a sentence, oisii desu would mean something like "It's tasty," "That's tasty," "Something's tasty," "She's tasty," "The property of being tasty exists at this moment." All of those things would be proper translations depending on the context.

In these cases, the ~i part is the actual part of the word that changes and the 'desu' is just on there to make it polite. The desu here is 100% just a politeness marker.

Sometimes you'll hear these called 'adjectives' but again they're not like adjectives in English so there's no real point in calling them such. The form/structure is what's important.

〇〇です タイプ
**** desu type

The third type of sentence/word is thing+desu. This desu is different from the previous one as in this one the desu IS the core part of the sentence. It's not just a politeness marker. Pretty much anything that doesn't fall into the previous two types is going to be this type. Depending on the context these things can be translated all different kinds of ways. Let's use the example 勉強です benkyou desu. Benkyou desu means 'study.' As a sentence on it's own it can mean "This is for study," "I am studying," "She studies that," "This is what I study," "A concept of study exists at this moment relevant to this context." It means study and the rest of what it means is completely dependent on context.

And again, other sources will call these "nouns" and lol that's not even close to what they are.

EXAMPLE TIME

For the sake of these examples we're gonna learn the word for yes. It's ええ ee. If you're answering a question that's yes/no, you're probably going to use ee and not 'hai' or whatever.

So let's say someone asks if you drink beer. You could answer

ええ、飲みます
ee, nomimasu

Good translations for this would be "Yeah, I do." or "Yeah, I drink beer." Even though we don't say "I" anywhere, and there's no word that means "do" in there. That's just how it works. This is an example of a ~masu type sentence.

If someone asks you how the weather is where you live:

暑いです
atui desu

"It's hot here." Even though we don't say a "here" word or whatever. All that is context. This is an example of an ~i desu sentence.

If someone asks you where you were born:

アメリカです
amerika desu

This could be translated as "I was born in America." Yup, none of those words are there except America, but the context makes the rest of it. This is an example of a ***desu type, or a something+desu type.

Negative Conjugations

So you want to say negatives and stuff, huh? Negatives are literally just the opposite or "no" version of stuff. Cold. Not Cold. Drink. Don't Drink. You get it.

To make a negative version of ~masu words, just change the ~masu to ~masen

分かりません
wakarimasen

"I don't understand."

To make a negative version of ~i desu words, the ~i part changes to ~kunai. The desu is just a politeness marker so you just add it to the end again.

寒くないです
samukunai desu

"It's not cold."

To make a negative of ***desu words, since the desu part is the core part, the desu changes to ではないです de wa nai desu. Yeah, it's a bit much. The "de wa" part is often shortened into じゃ zya. So you get "zya nai desu" Usually the "de wa" is used in writing and "zya" is used in speaking.

An even more polite way to say this same thing is ではありません de wa arimasen. Here you can also shorten de wa to zya.

勉強ではありません
benkyou de wa arimasen

勉強じゃないです
benkyou zya nai desu

"It's not study" lol whatever you get it. Like if you were reading a novel for fun and someone asked you if it was for class. "No, this isn't for study." Get it??

The most important thing

The most important thing to take away from this is that there is NO JAPANESE WORD FOR AM, IS, ARE, WAS, WERE, ETC. Those are English things ONLY. Don't try to "translate" English into Japanese because it does not work. Don't think of "How do I say 'it is cold' in Japanese?" because you're thinking of English. Just know what samui desu is and that it refers to a state of being cold. There's no REAL English equivalent.

Metapod JP crash course P2: Perfective Tense

So we're going to learn about a tense that's called various things, like perfective or whatever. Japanese doesn't really have present and past tenses like English. This tense rather refers to actions that are completed. While generally things that have completed are in the past, it doesn't always correlate with English past tense as things can be completed in the present and that's the more important part. But the point is that the thing is ALL DONE.

~masu types

To make this form of ~masu type, you change the ~masu to ~masita. Here's where we'll see an example of this perfective tense meaning something that is 'present tense' in English.


分かりました
wakarimasita

"I understand." Yup, it's the same translation as 'wakarimasu!'

'wakaru' refers to the concept of understanding, in the sense that you are making use of your brain to actively make sense of or work something through. You use 'wakarimasu' to say you understand a language because processing language is an ongoing thing. It's not completed. You're not like... done processing English or Japanese or something.

But in the case of 'wakarimasita' we refer to the act of having processed something having finished. Like if someone gives you an order at work like "Go deliver these papers to the engineering department" you would respond with wakarimasita. Because you have already finished the contemplating part. You're not like, still trying to figure out what you need to do. This is again because Japanese words are not English words and they don't actually translate like that.

~i desu types

To make the perfective of ~i desu type of words, you change the ~i to ~katta. The desu again is just a politeness marker and the ~i is the actual part that is changing.

寒かったです
samukatta desu

"It was cold," obviously you would only say it when it's no longer cold, because concept of cold has to be finished/completed. It's a little more straightforward to translate to English, but again don't think of it like English.

よかったです
yokatta desu

"That's good," because the thing that was good has been finished. Like if someone dodged an oncoming car. But if you're talking about the weather, you would use the normal form いいです ii desu because the weather is still ongoing and hasn't stopped being good.

***desu type

With these, the desu is the main part. でした is the new form here.

勉強でした

It was study. This isn't really a great example of desita but you get it. I just wanted to use the same word.

A lot of times in English we'll use "past tense" for stuff because it already "happened" or whatever, but if the concept hasn't stopped, don't use ~desita. This is really just something you have to get a feel for. Pay attention to how other people say stuff and think about why they use one or the other.

Whatever you don't DON'T equate these things to "past tense" or whatever in English. The key part is that the concept has ceased to be ongoing.

Negative versions!

Again negative is just the opposite. I ate. I didn't eat. Yup. Again, it doesn't always refer to things in the past. So this is when the thing that didn't happen is done not happening lol. It's a little more difficult to put into English words, but if you get the previous part you should be able to get this.

~masu becomes ~masen desita

Easy.

The next is interesting. Remember how the negative of ~i desu things is ~kunai desu? Well that ~kunai part is also an ~i thing. So to make the perfective version of that negative you change THAT ~i to ~katta. Or in other words, the ~i desu becomes ~kunakatta desu. It's kind of long, but you can also think of it as the ~katta version of ~kunai. Get it???? Well, that's just a way to remember it. Just know that ~i becomes ~kunakatta. And of course you add the desu part at the end as the politeness marker again.

Lastly you have the ****desu ones. If you remember the normal negative forms:

~de wa arimasen
~de wa nai desu

These are actually a ~masu thing and an ~i desu thing. So you can just make the perfective forms of those

~de wa arimasen desita
~de wa nakatta desu

And of course you can shorted de wa to zya

~zya nai desu
~zya arimasen desita

Recap

So we have three different types of words/sentences. And each of these we have four conjugations (kind of more for the ***desu things).

Think about what situations these would make sense for without thinking of what it would mean in English. Keep in mind whether or not something has finished/completed, and whether it's positive or negative.

wakarimasu
wakarimasita
wakarimasen
wakarimasen desita

samui desu
samukatta desu
samukunai desu
samukunakatta desu

benkyou desu
benkyou zya nai desu
benkyou desita
benkyou de wa arimasen desita

Practice thinking of things people could ask you that you would respond to in these different ways and why. Again, don't think of English or whatever other language. Just think of the concepts.

Metapod JP crash course part 3: particle fun

So you want to say sentences that are more than one word huh?! To do this you start with your one-word sentence and attach things before it with particles. Particles show how another word relates to the final part of the sentence.

Let's look at 飲みます nomimasu. It refers to the act of drinking (or rather swallowing without chewing, like with medicine). We'll see how different particles can link things to it.

o

The particle "o" (note that this is written with the kana を, not the 'normal' o kana) links things to the end by showing that they are the recipient or the thing being acted upon. So in the case of drinking, this would be the thing being drunk.

お茶を飲みます
ocha-o nomimasu
refers to drinking tea (ocha = tea)

ビールを飲みます
biiru-o nomimasu
refers to drinking beer (biiru = beer)

GET IT?

The o particle only links with ~masu type things.

ga

The particle "ga" generally refers to the 'subject' of the thing. The thing that is doing or being.

客が飲みます
kyaku-ga nomimasu
refers to a customer/guest who is doing some drinking (kyaku = customer)

天気が寒いです
tenki-ga samui desu
refers to the weather being cold! (tenki = weather)

映画が勉強です
eiga-ga benkyou desu
refers to a situation in which a movie is used as study (eiga = movie)

Pretty simple. Sometimes this doesn't correspond with English subjects.

日本語が分かります
nihongo-ga wakarimasu
(nihongo=Japanese language)

In this case, wakarimasu refers to understanding going on, in the sense of something being broken up into pieces to be understood. In English we thinking of understanding as happening TO something, but in Japanese the 'breaking up' is what the thing is doing.

In fact, you'd use more than one ga because the thing doing the breaking up can be both the thing being understood and the thing doing the understanding:

私が日本語が分かります
watasi-ga nihongo-ga wakarimasu

Fun right?

With ~i desu type sentences this is almost always the case:

ゾウが鼻が長いです
zou-ga hana-ga nagai desu
(zou = elephant, hana = nose, nagai = long)

Elephants have long noses. Note that we're not using some Japanese version of the English word "have" because Japanese is not English. It doesn't work that way. And yes, I'm going to stress over and over that Japanese and English are not some kind of cipher where you can just take an English sentence and sub out the words for Japanese ones. You have to really change the way your brain thinks about putting thoughts together and use this new system to format it. Fun!

de

The particle 'de' marks something that is the means or method or vessel or whatever by which the thing happens or is done or whatever.

車で行きます
kuruma-de ikimasu
refers to going by means of a car (kuruma = car, ikimasu = go)

Using multiples

Basically to make Japanese sentences, you just have your main sentence thing, and then before it put things+particles to show how they relate to it. To use multiples at once you just ... do multiples! Easy.

客がコップでビールを飲みます
kyaku-ga koppu-de biiru-o nomimasu

Here nomimasu is our main thing, the drinking. The person doing the drinking is a customer (kyaku) so we use kyaku-ga. A cup (koppu) is the vessel through which drinking is taking place, so we use koppu-de. And beer is the thing being drunk so we use biiru-o.

Unlike English where you need to do things in a certain order because the order changes in the meaning, here in Japanese, the particles dictate the meaning so the sentence is grammatical no matter the order.

kyaku-ga biiru-o koppu-de nomimasu
koppu-de kyaku-ga biiru-o nomimasu
koppu-de biiru-o kyaku-ga nomimasu
biiru-o koppu-de kyaku-ga nomimasu
biiru-o kyaku-ga koppu-de nomimasu

They're all grammatically sound. Generally whatever you put first is the most stressed things. So if you're like surprised or it's important that they're using cups specifically to drink beer (I mean, that's kinda weird, right?) then putting "koppu-de" first is more natural.

Generally if there's no stress, it's most natural to put the thing with -ga first and then the rest of the stuff doesn't really matter. Just say it in the order it comes to your head first honestly.

Sentence-ending particles

There are also some particles that come at the end of sentences instead of after words to relate them to the ending part.

Here's some examples:

ka

'ka' makes the sentence into a question. Pretty simple stuff. You don't change around the order of the words or whatever like in English. Just say the same thing but with 'ka' at the end.

ビールを飲みますか
biiru-o nomimasu ka

Asking if the act of drinking is done to beer. Depending on the context can be translated to various things like "Is it beer they're having today?" or "Are you a drinker?"

yo

'yo' is used when you're presenting new information. You're making the assumption that the other person doesn't know the thing that you're saying and you're giving them this new information. Often this is only used when the person is specifically asking for new information or they believe something else that's wrong or something. Basically only if it's OBVIOUS that they don't know by both of you and you're giving brand new info.

Because of this, it can also be used to stress what you're saying or give extra emphasis. Kinda like an exclamation mark in English lol. But be careful with using it because it can sound like you're talking down to someone like implying they don't know stuff lol.

ビールを飲みますよ
biiru-o nomimasu yo

So like if someone asked you "Hey, do you know what they're drinking in there?" you could respond biiru-o nomimasu yo. The yo is because you're giving them the new information.

Also if you just happened to see some people drinking and were like super excited or surprised by this fact, you could say the same and it would be like "Wow, they're drinking beer!!" hahaha.

ne

'ne' is used when you're assuming the other person does know the thing you're saying. It can be used to request confirmation of something if you're not sure, or just to share information you know is already known, like to be conversational or whatever.

ビールを飲みますね
biiru-o nominasu ne

So like if you needed to check what the customer is having, and you say this to the other server, you're asking to confirm that the information is properly known. "They're having beer, right?" or even just "Are they having beer?" as you see, it's a question in this case, but we're not using ka, because the situation is different than just asking a straight question, because Japanese is not English.

You could say the same if you both knew someone was drinking and you just wanted to comment on it. Like if your dad always has a beer when he gets home from work and you wanted to comment on it to someone else in your family who also knows he does this you could say it like this. It's hard to come up with a good example of how this works, but it's pretty easy to pick up if you just listen to how other people are using it.

Summary

Basically all sentences are just

[thing-particle] [thing-particle] [main thing]

With as many thing-particles as you need. Remember if something is obvious from context and you're not meaning to stress it for any reason, just don't say it. Like in the former context of you're serving a customer and you ask the other server if they're drinking beer, if it was already obvious who you would be asking about, you wouldn't need the kyaku-ga part. Just say nomimasu ne.

A　「客がビール飲みますか」
B　「ええ、飲みますよ」

A: kyaku-ga biiru-o nomimasu ka
B: ee, nomimasu yo

In this exchange, person A asked the other person B if the customer was having beer. When they responded, because of what was asked, it was obvious that they were talking about the customer and beer so all they had to say was nomimasu yo. And since the A person directly asked for new information, B uses yo at the end.

Note that in writing, since ka makes it obvious it's a question, you don't need to use a question mark. But you can use one if you want.

Note that there are way more particles than this, these are just some examples.

Metapod JP 4: wa and mo

This time we're going to talk solely about two particles. Let's keep talking about beer.

ビールを飲みます
biiru-o nomimasu

By now you should realize that this refers to some act of drinking being done upon a thing called beer, which can be all kinds of situations depending on the context. And we use o attached to biiru to show its connection to the nomimasu.

There are two particles that can replace the o to give extra context to the example. Let's look at mo first:

mo

'mo' can replace 'o' in this case to show that beer is being drunk in addition to other things. There's some set of things that are having drinking done upon them, and beer is included in this set. The most important thing here is inclusion.

ビールも飲みます
biiru-mo nomimasu

He's having beer, too.
There's also beer being served.
I also drink beer.

Get it? In English we add words like "too" and "also" and stuff to show inclusion to other things, but in Japanese you replace o with mo.

You can also replace ga with mo:

客がビールを飲みます
kyaku-ga biiru-o nomimasu

For when the customer is drinking beer, just plain statement.

客もビールを飲みます
kyaku-mo biiru-o nomimasu

Here the kyaku/customer is being included with some kind of group. So maybe some other people are having beer and you want to say that that customer is also having beer, in addition to the other things/people/whatever that are also having beer.

'ga' and 'o' are the only things you replace with 'mo.' For other things, you just add 'mo' to the existed particle:

車でも行きます
kuruma-de-mo ikimasu

Some kind of going is happening by various vessels, and one of those vessels includes a car. "We're also taking cars." "I also commute by car." That kind of thing.

wa

'wa' is the harder of the two to understand, but it's basically the opposite of 'mo.' It shows exclusion. There's some set of things, and you're commenting on only the thing you're using wa for.

But it doesn't mean 'only.' It refers to the fact that you're not referring to other things.

(Also note this 'wa' is said as 'wa' but you use the kana は to represent it)

ビールは飲みます
biiru-wa nomimasu

There is some kind of act of swallowing without chewing taking place, and in this action, the recipient of the swallowing is beer. But there may or may not be other things, we're only talking about beer here.

So maybe your customer has ordered a few things, but you only remember that he ordered beer, and you're telling someone that. You'd use 'wa' because it's the only thing from the set you're commenting on. You're not saying that he's only drinking beer, you're saying that beer is the only thing from the set of things you're referring to at the moment. You're excluding it from the other things in your statement and showing it stands apart in your knowledge.

"He's at least having beer, but I don't know what else." Yeah, all of that meaning is packed into that 'wa.' It's hard to get a handle on.

Another example, let's say there was a room of people in Japan, and someone came in because they needed an English translator, and they come into the room and ask if anyone in here speaks English. You would respond with:

私は分かります
watasi-wa wakarimasu
(watasi=referring to yourself)

You would use watasi-wa and not watasi-ga because you're only commenting on yourself, not anyone else. There's a group of people, but you're only speaking for yourself. You don't know if anyone else here knows English, or maybe you do, but you're not talking about them, only yourself, you're setting yourself apart in what you're talking about.

If you were to say watasi-ga, you'd be making a statement that you ARE the one who knows English. Now, if the context was that every person in the room was brought in because each one knows a different language, and the person came in to ask which one of you were the one person who knew English of the group, you'd use watasi-ga because you're not concerned with making sure you're saying you're not commenting on anyone else, there's no exclusion to be had there.

Because of this type of meaning, -wa is also used to bring up new topics of conversation.

客はビールを飲みますか
kyaku-wa biiru-o nomimasu ka

In this case, if you weren't talking about the customer before, but you want to bring them up, you'd use kyaku-wa. Kind of like "As for the customer..." I guess. New topics always get the -wa, because you're excluding them from all other topics that may be talked about.

Just like -mo, -wa is used to replace -ga or -o. With other stuff, you just add it on to the existing particle:

車では行きません
kuruma-de-wa ikimasen

There's not any going happening by means of a car, but there may be going being done by other things, but you're only commenting on your knowledge that it's specifically cars that are not doing the going out of all the things, and you're not saying that not going is not being done by other things.

"I know at least they're not taking a car, but I'm not sure what they're actually taking" or "He commutes, but not by car."

As you can see with these and previous examples throughout, Japanese does not translate literally into English whatsoever. If you try to say "the word 'kedo' means 'but' in Japanese!" and then try to translate "He commutes, but not by car," you'd be really fucking wrong trying to say something like 'ikimasu kedo kuruma zya nai desu.' That doesn't even make sense. You can't just take an English sentence and try to substitute in Japanese words. It just doesn't work that way.

And some other random particles

に
-ni is used to show a relationship of where the final thing ends up. Like the destination.

nihon-ni ikimasu

Refers to going to Japan.

へ
-e (written with kana へ) shows a relationship of the thing being where the final thing is moving or happening toward.

nihon-e ikimasu.

Refers also to going to Japan. You can say either in this case.

But for something like writing on paper:

紙に書きます

kami-ni kakimasu
(kami = paper, kakimasu = writing)

The final destination of the writing action is on the paper. You don't write like... AT a paper or TOWARD a paper. So you don't say kami-e ever in this case.

から
-kara shows the place from where the thing is happening or whatever.

アメリカから日本へ行きます
amerika-kara nihon-e ikimasu

Going from America to Japan. Easy right? You can use for things other than 'going':

盾を宝箱から引き出しました
tate-o takarabako-kara hikidasimasita
(tate = shield, takarabako = treasure chest, hikidasimasu = to pull/grab out)

I took the shield out of the treasure chest.

Again, notice we're using completely different English for all of these examples even though the Japanese structure is the same. So it's important not to think of Japanese as "meaning" things in English, but rather understand the structure and how it works without relating it to English at all.

And like the others, you can add -mo or -wa to these as needed:

日本にも行きます
nihon-ni-mo ikimasu

Also going to Japan (in addition to other places going to)

日本へは行きません
nihon-e-wa ikimasen

Not going to Japan (but possibly going to other places, not commenting on those)

日本からも行きました
nihon-kara-mo ikimasita

Also came from Japan (in addition to other places things/people had come from)

JP crash course masterpost

Gonna try to keep all these here so you can just bookmark this page to reference them all:

Part 1: The three types of sentence and their negatives
Part 2: Perfectives (things that already concluded)
Part 3: Particles (how to make more than one-word sentences)
Part 4: -wa and -mo and a few other particles
Part 5: Plain form and multiple sentences together
Part 6: Describing things with an entire sentence
Part 7: te form (sequence, commands, trying, etc.)
Part 8: Conditionals

Japanese with Pokey

Page 1
Page 2

JP5: Without desu-masu

So far we've been doing everything in desu-masu form, the polite language. But when we want to start to make more complicated sentences, we're going to need to understand the 'plain' form of things, because when they don't come at the end of sentences, things get used in this way. It's a bunch of fun. It's really not that hard, there's just kind of a lot of forms you have to learn when it comes to the ~ru (~masu) words.

Also, when you look words up in the dictionary, this is the form they'll be in. It's also the forms you'll use when talking to close friends in casual settings. I tend to swap between desu-masu and plain form a lot because desumasu is shoved down your throat so it becomes more natural because it's how you'll talk to pretty much anyone except your buds, and most people learn Japanese for the sake of travel/study/work/whatever where they'll be talking to strangers and coworkers and etc.

Anyway...

Let's start with the easiest one of our three word/sentence types:

Plain form of いです ~i desu

I told you before that the 'desu' in ~i desu type sentences/words is just a politeness marker. Well you're in luck, because the plain form of ~i desu words you just don't say desu. Yup.

寒い
samui

cold.

So easy!

ゾウが鼻が長い
zou-ga hana-ga nagai

Elephants have long noses. Woop woop.

All the other forms, again, just drop desu.

今日は暑くない
kyou-wa atukunai

Not hot today (not referring to other days)

昨日も寒くなかった
kinou-mo samukunakatta

Wasn't cold yesterday, either

Plain form of 〇〇です ***desu

This one is pretty easy too. Remember how I said the 'desu' was the actual important part that changes in this, and not just a politeness marker? That's because 'desu' in this case is the desu-masu form of 'da.'

勉強だ
benkyou da

study

See! Easy. And the plain form of でした desita is だった datta.

勉強だった
benkyou datta

that was informative

Get it?

As for the negatives, they were actually just ~i type things anyway, so you just drop that desu:

benkyou zya nai
benkyou zya nakatta

You can still say de wa if you want, especially in writing that's normal. But arimasen and arimasen desita are desu-masu things too so we don't use them in plain form.

Plain form of ます ~masu types

This is the fun one. Actually, only the perfective form is really "hard" and just because there's lots of forms.

In their plain form, ~masu words end in something with an u sound in it. Like ru, su, tu, ku, etc. Or sometimes just u itself. You can easily figure it out if you know the ~masu form, as you pretty much just get rid of the ~imasu part and change it to ~u.

So like:

wakarimasu > wakaru
nomimasu > nomu
ikimasu > iku

Simple, right? There's also some things that end in imasu or emasu and they turn into ru:

tabemasu > taberu

With the emasu ones it's obvious because there's no 'i' before the 'masu,' but with the ones that actually go from 'imasu' to 'iru' you just have to kind of ... know. The same in reverse, if you know it ends in 'iru,' you can't tell right away if it's going to be 'irimasu' that it changes to or just 'imasu.' A dictionary will tell you, and as you're picking up words you'll see how it's used and it will become obvious.

But basically the point is they end in something-u.

Now to make the negative of this, you just change that ~u to ~anai

wakaranai (don't understand)
nomanai (don't drink)
ikanai (don't go)

There's an exception here with things that end in just plain う u. This is a remnant of older Japanese; they're actually like ending in "wu" but there's no "wu" anymore. So they become "wanai" at the end instead of "anai"

tigau > tigawanai

like that

And in the case of those special eru/iru things where the whole ru gets changed to masu, you change the ru to nai in this case too:

tabenai (don't eat)
minai (don't look)

Pretty easy.

And then to make perfective negative of those, you'll notice they have now become ~i things. So just change the ~i to ~katta like before.

wakaranakatta (didn't understand)
nomanakatta (didn't drink)
ikanakatta (didn't go)
tabenakatta (didn't eat)

But just regular perfective is the hard part. Because it depends on which type of something-u we're going with.

u becomes tta
ku becomes ita
gu becomes ida
su becomes sita
tu becomes tta
mu becomes nda
ru becomes tta

and in special eru/iru cases, the ru is dropped in place of just 'ta' (NOT 'tta')

wakaru > wakatta (understood)
kaku > kaita (wrote)
oyogu > oyoida (swam)
dasu > dasita (came out)
matu > matta (waited)
sumu > sunda (lived)
tigau > tigatta (was different)

Sentence-connecting particles kara and kedo

So we learned sentence ending particles ka, yo, and ne before. Now we can add a particle to the end of a sentence to connect it to another sentence. When you're doing this, you use the plain form on the first sentence. Only the final part of the final sentence would you use desu-masu form unless you're being ridiculously polite which is something you'll only hear in anime or whatever and probably never use in real life. Maybe like some super formal political thing? Chances are you won't ever say it yourself. Except by accident.

We'll start with kara.

'kara' is added to the end of one sentence to show that it's the cause or reason for the second.

飲みすぎたから病気です
nomisugita kara byouki desu
(nomisugiru = overdrink, byouki = sickness)

I drank too much so I'm sick.

let's thow a bunch of other words in there to show you how more complex sentences look:

昨日、バーでビールを飲みすぎたから今は病気です
kinou, baa-de biiru-o nomisugita kara ima-wa byouki desu
(kinou = yesterday, baa = bar, ima = now)

Yesterday I drank too much beer at the bar so now I'm sick.

Notice how even though there are a lot of words there, it's still just the basic old sentences. Thing-particle thing-particle main thing. Then put two sentences together with kara. Easy.

Next we'll do kedo, which shows that the second sentence happens despite the first.

飲みすぎたけど病気じゃないです
nomisugita kedo byouki zya nai desu

He overdrank but he's not sick.

And if you've noticed, nomisugiru is one of those special iru/eru words lol.

Let's try with some other stuff:

泳いだから髪を浸した
oyoida kara kami-o hitasita

I was swimming so my hair got wet.

命令が分かったけど出来ませんでしたよ
meirei-ga wakatta kedo dekimasen desita yo

She understood her orders but wasn't able to follow through.

眠いから車で行きませんか
nemui kara kuruma-de ikimasen ka

Are you not driving because you're tired?