Japan has a large number of different conjugations for verbs. First there are polite and plain forms of verbs. Polite forms are used when speaking to elders or people who you are unfamiliar with. Plain forms are used for speaking to longtime friends and people who you are comfortable with. In addition, plain forms are also used for many other grammatical usages that we will cover in later lessons.
Then a verb also conjugates depending on whether it is affirmative or negative.
A third aspect of the verb that determines how a verb is conjugated is whether the verb is past or present tense.
The final aspect is what class the verb belongs to. There are 3 classes of verbs that also determine how the verb is conjugated.
As you can imagine, conjugating verbs in Japanese is very difficult because of all these factors and will require a lot of memorization and practice.
First let's figure out what the verb classes
As mentioned before, there are 3 classes of verbs, class 1, class 2, and class 3.
Class 1 verbs (in dictionary form) have different endings and roots, for example 聞く (to listen).
Class 2 verbs (in dictionary form) have different roots and all end with the same ending る (ru) for example 食べる (to eat).
Class 3 verbs (in dictionary form) are irregular verbs. For a beginner you only need to know する(to do) and 来る (to come).
Now let's start learning verb conjugations with the most basic form of verbs.
PRESENT TENSE FORMS
Form #1 - Present Plain Affirmative - DICTIONARY FORM
The examples I showed you above are the dictionary form (how you'll find the verb in a dictionary). It is the equivalent to the infinitive form in english. Dictionary form is also the same as the present plain affirmative. It is composed of a root and an ending. Let's take a look at how the dictionary form is used.
Class 1 verb
Class 1 verbs all have different endings.
聞く - to listen (kiku)
root - 聞
ending - く
洗う - to wash (arau)
root - 洗
ending - う
話す - to speak (hanasu)
root - 話
ending - す
立つ - to stand (tatsu)
立 - root
つ - ending
読む - to read (yomu)
読 - root
む - ending
ある - to exist (aru)
あ - root
る - ending
およぐ - to swim (ayogu)
およ - root
ぐ - ending
Class 2 verb
All class 2 verbs have an ending of る.
to eat - 食べる (taberu)
root - 食べ (tabe)
ending - る (ru)
to watch - 見る (miru)
見 - root (mi)
る - ending (ru)
Form #2 - Present Plain Negative - NAI FORM
The present plain negative is used to say that you are NOT doing an action in the present-tense. Also this is used for informal situations (plain form means informal), so when you are talking to your buddies you can use this form.
Also think of this form as the "nai" form because all the endings will have ない(nai) which is a negative marker.
[Verb root + A-version End + nai(ない)]
Take the verb's root, add the A-version of the ending, and append ない
(what is A-version? Basically every root that is class 1 dictionary form is a U-version because it sounds like a syllable + u, a version is the same syllable + a) Some examples are below.
読む becomes 読まない
As you can see, YOMU becomes YOMA NAI.
The part that you should look at is the transition from YOMU to YOMA. The U sound became an A sound.
Then we add a nai (ない）at the end.
書く(kaku - to write) becomes 書かない (kakanai)
聞く(kiku - to listen) becomes 聞かない (kikanai)
泳ぐ(oyogu - to swim) becomes 泳がない (oyoganai)
[form using verb root and add nai (ない)]
食べる(食べ [tabe] is the root) becomes 食べない(tabenai)
Class 3 - irregular - memorize the following
来る(kuru) becomes 来ない(konai)
する(suru) becomes しない(shinai)
Form #3 - Present Polite Affirmative - MASU FORM
This is used with elders and people you just met to talk about actions in the present. Think of this as the "masu" form because every ending has ます(masu) which is the polite marker.
[root of verb + i-form of ending + masu]
Notice that the root of the dictionary form usually has a U sound and it becomes an I sound when you make it to the masu form.
飲む (nomu) becomes 飲みます (nomimasu)
聞く (kiku) becomes 聞きます(kikimasu)
[root of verb + masu]
食べる becomes 食べます
来る becomes 来ます
する becomes します
Present Polite Negative - MASEN form
Everything is exactly the same as the MASU form, except you will have MASEN instead of MASU.
PAST TENSE FORMS
Form #1 - Past Plain Affirmative - TA FORM
If you are talking to your buddies in an informal situation about events in the past, use the TA form, called the TA form because of the TA at the end (た)
[root + ita]
書く (kaku) becomes 書いた (kaita)
聞く (kiku) becomes 聞いた (kiita)
[root + ta]
食べる (taberu) becomes 食べた (tabeta)
来る (kuru) becomes 来た (kita)
する (suru) becomes した (shita)
Form #2 - Past Plain Negative - nakatta FORM
[root + A-form of ending + nakatta]
聞く (kiku) becomes 聞かなかった (kikanakatta)
書く (kaku) becomes 書かなかった (kakanakatta)
[root + nakatta]
食べる (taberu) becomes 食べなかった (tabenakatta)
来る (kuru) becomes 来なかった(konakatta)
する (suru) becomes しなかった(shinakatta)
Form #3 - Past Polite Affirmative - mashita form
[root + i-form of ending + mashita]
書く (kaku) becomes 書きました (kakimashita)
聞く (kiku) becomes 聞きました (kikimashita)
[root + mashita]
食べる (taberu) becomes 食べました (tabemashita)
来る (kuru) becomes 来ました (kimashita)
する (suru) becomes しました (shimashita)
Form #4 - Past Polite Negative - MASENDESHITA form
[root + i-form of ending + masendeshita]
聞く(kiku) becomes 書きませんでした (kikimasendeshita)
書く (kaku) becomes 書きませんでした (kakimasendeshita)
[root + masendeshita]
食べる (taberu) becomes 食べませんでした (tabemasendeshita)
来る (kuru) becomes 来ませんでした (kimasendeshita)
する (suru) becomes しませんでした (shimasendeshita)
Here's a great website with a chart to help you memorize conjugating verbs