Plain Form Overview | Japanese Casual Speech

What is the Plain Form?

The plain form isn't a single conjugation. It's a system of four forms that together cover all basic tenses in casual speech. It's the informal counterpart to the polite (ます) system.

	Affirmative	Negative
Non-past	Dictionary form (食(た)べる)	Nai-form (食(た)べない)
Past	Ta-form (食(た)べた)	Nakatta-form (食(た)べなかった)

That's the whole casual verb world in one table. Learn these four conjugations and you can express anything in informal Japanese.

When to Use Plain Form

1. Casual Conversation

With friends, family, close colleagues. Anyone you're not being formal with:

何(なに)食(た)べる？ (What are you eating?)
昨日(きのう)見(み)た？ (Did you watch yesterday?)
行(い)かない。 (I'm not going.)

2. Inside Grammar Patterns (Even in Polite Speech!)

This is crucial: even when your sentence ends politely, subordinate clauses use plain form:

映画(えいが)を**見(み)た**と言(い)いました (Said he watched a movie)
食(た)べないほうがいいです (It's better not to eat)
行(い)くつもりです (I intend to go)
おいしかったと思(おも)います (I think it was delicious)

The grammar pattern attaches to plain form; the sentence-final form determines overall politeness.

3. Internal Monologue / Diary

When you think to yourself or write casually, plain form is natural:

疲(つか)れた... (I'm tired...)
明日(あした)何(なに)しよう。 (What should I do tomorrow.)

Plain Form vs Polite Form

Plain	Polite	Meaning
食(た)べる	食(た)べます	eat / will eat
食(た)べない	食(た)べません	don't eat
食(た)べた	食(た)べました	ate
食(た)べなかった	食(た)べませんでした	didn't eat

Same meanings, different social register. The choice between plain and polite has zero effect on the factual content. It only signals the relationship between speaker and listener. Our lesson on formal vs. casual speech covers when and how to switch between the two registers.

Plain Form for All Verb Types

U-verbs (using 飲む as example)

	Affirmative	Negative
Non-past	飲(の)む	飲(の)まない
Past	飲(の)んだ	飲(の)まなかった

Ru-verbs (using 見る as example)

	Affirmative	Negative
Non-past	見(み)る	見(み)ない
Past	見(み)た	見(み)なかった

Irregular (using する as example)

	Affirmative	Negative
Non-past	する	しない
Past	した	しなかった

Common Grammar Patterns that Use Plain Form

〜と思(おも)う (I think ~): 明日(あした)雨(あめ)が降(ふ)ると思(おも)う
〜と言(い)う (say that ~): 彼(かれ)は来(こ)ないと言(い)った
〜つもり (intend to ~): 日本(にほん)に行(い)くつもり
〜ことがある (have experienced ~): 富士山(ふじさん)に登(のぼ)ったことがある
〜前(まえ)に (before ~): 寝(ね)る前(まえ)に歯(は)を磨(みが)く
〜後(あと)で (after ~): 食(た)べた後(あと)で散歩(さんぽ)する

Example Sentences

今日(きょう)何(なに)する？ (kyou nani suru?) — What are you doing today?
昨日(きのう)の映画(えいが)見(み)た？ (kinou no eiga mita?) — Did you watch yesterday's movie?
まだ食(た)べてない。 (mada tabetenai.) — I haven't eaten yet.
彼(かれ)が来(く)ると思(おも)う。 (kare ga kuru to omou.) — I think he'll come.
日本(にほん)に行(い)ったことがある。 (nihon ni itta koto ga aru.) — I've been to Japan.
全然(ぜんぜん)知(し)らなかった。 (zenzen shiranakatta.) — I had no idea.
寝(ね)る前(まえ)にシャワーを浴(あ)びる。 (neru mae ni shawaa wo abiru.) — I shower before bed.
そんなこと言(い)わないで。 (sonna koto iwanaide.) — Don't say things like that.