Plain form is also called dictionary form and it is just like “masu” form but is used in casual, informal situations. Plain form is the present/future tense and is pretty important because you use this as a basis to create other verb forms (like past and negative).
You can practice all of these using the J-Talk Online Memrise course Beginners Japanese Grammar 1 (JLPT N5 Grammar). See last week’s post on Studying Japanese Grammar for tips on ways to learn grammar.
But the first thing you need to know about plain form are the 3 groups.
Group 1 or “u verbs”
These are words that have an “u” sound at the end. When you turn a “masu” form into plain form the “I” changes to the “u” for group 1 verbs. Such as the following.
いきます ikimasu -> いく iku = to go
あらいます araimasu -> あらう arau = to wash
たちます tachimasu -> たつ tatsu = to stand
はなします hanashimasu -> はなす hanasu = to talk
かえります kaerimasu -> かえる kaeru = to go home
はしります hashirimasu -> はしる hashiru = to run
Group 2 or “ru verbs”
This group can be distinguished by the “e” sound in “masu form”. To change it to plain you just remove the “masu” to make it into a stem and add “ru”. These verbs are easier because unlike Group 1 the stem doesn’t change at all.
たべます tabemasu -> たべる taberu = to eat
しめます shimemasu -> しめる shimeru = to shut
ねます nemasu -> ねる neru = to sleep
いれます iremasu -> いれる ireru = to put in
I mentioned that group 1 verbs can be recognised by the “i” before the “masu”. There are a few group 2 verbs that have this pattern too, you just have to remember them and get used to using them as group 2 and not group 1 verbs:
います imasu – いる iru = to be
かります karimasu – かりる kariru = to lend
おきます okimasu = おきる okiru = to wake/get up
Group 3 (irregular verbs)
There are only 2 verbs. They are irregular because they change differently from groups 1 and 2.
します shimasu -> する suru = to do
きます kimasu -> くる kuru = to come
As I said, these groups are particularly important to learn because each group changes differently depending on what you’re turning the verb into. The following explains past tense and negative to illustrate these changes. Pay particular attention to group 1/U verbs as they change the most.
Plain past form is done by removing “ru” and adding “ta” to the end of the word. But this is different for each group.
This is a bit of a weird one because depending on the “u” ending they get turned into past tense in different ways.
う (u), つ (tsu), or る (ru) change to った. Such as:
かう kau -> かった ka-ta = to buy / bought
まつ matsu -> まった ma-ta = to wait / waited
かえる kaeru -> かえった kae-ta = to go home / went home
む (mu), ぬ (nu), or ぶ (bu) change to んだ. Such as:
よむ yomu -> よんだ yonda = to read / read
しぬ shinu -> しんだ shinda = to die / died
あそぶ asobu -> あそんだ asonda = to play / played
And く(ku) changes to いた. Such as:
かく kaku -> かいた kaita = to write / wrote
EXCEPT いく (to go) which changes to いった (went).
This is simple as you don’t change the stem of the word and just add た. Such as:
たべる taberu -> たべた tabeta = to eat / ate
する suru -> した shita = to do / did
くる kuru -> きた kita = to come / came
You can make these more polite by adding “desu”. I.e いったです instead of いきました is slightly less formal. BUT NEVER mix た and でした (i.e いったでした)! And NEVER mix plain and です (i.e いくです)!
To make a word negative in plain form you add “nai” ない
For group 1/”u” verbs you change the “u” to an “a” sound and add “nai”.
いく iku -> いかない ikanai = to go / do not go
あそぶ asobu -> あそばない asobanai = to play / do not play
Remove the “ru” of the “ru” verb and just add nai.
たべる taberu -> たべない tabenai = to eat / do not eat
しめる shimeru -> しめない shimenai = to close / do not close
Irregulars have their own changes. Be careful of “kuru” because it changes to “KOnai”
する suru -> しない shinai = to do / do not do
くる kuru -> こない konai = to come / do not come
You can practice all of these using the J-Talk Online Memrise course Beginners Japanese Grammar 1 (JLPT N5 Grammar)