Plain/Dictionary Form in Japanese

Overview

The plain form (also called the dictionary form for the present affirmative) is the base form of Japanese verbs as they appear in the dictionary. It is the casual counterpart of the polite ます form and is used in informal speech, inside embedded clauses, and as the building block for many grammatical structures.

At the A2 level, mastering the plain form is a major milestone. Until now, you may have relied on ます forms for everything. Learning the plain form unlocks casual conversation with friends, the ability to form relative clauses, quotations, and a wide range of intermediate grammar. It is not just "casual Japanese" — it is structurally essential.

How It Works

The four plain forms

Every verb has four plain forms:

Form	Ichidan (食べる)	Godan (行く)	する	来る
Present affirmative	食べる	行く	する	来る (くる)
Present negative	食べない	行かない	しない	来ない (こない)
Past affirmative	食べた	行った	した	来た (きた)
Past negative	食べなかった	行かなかった	しなかった	来なかった (こなかった)

Adjective and noun plain forms

Type	Present aff.	Present neg.	Past aff.	Past neg.
い-adjective	高い	高くない	高かった	高くなかった
な-adjective	静かだ	静かじゃない	静かだった	静かじゃなかった
Noun + copula	学生だ	学生じゃない	学生だった	学生じゃなかった

Where plain form is required

Context	Example
Casual speech	明日、何する？ (What are you doing tomorrow?)
Before と思う (I think)	雨が降ると思う (I think it will rain)
Before と言う (to say)	行くと言った (said they'd go)
Relative clauses	昨日買った本 (the book I bought yesterday)
Before から/ので (because)	忙しいから... (because I'm busy...)
Before とき (when)	暇なとき (when I'm free)
Before ことができる (can)	泳ぐことができる (can swim)

Examples in Context

Japanese	English	Note
食べる / 食べない / 食べた / 食べなかった	eat (all four plain forms)	Ichidan verb
行く / 行かない / 行った / 行かなかった	go (all four plain forms)	Godan verb
明日、何する？	What are you doing tomorrow?	Casual question
これ、知ってる？	Do you know this?	Casual (with ている contraction)
雨が降ると思います。	I think it will rain.	Plain form + と思う
昨日食べたラーメンはおいしかった。	The ramen I ate yesterday was delicious.	Relative clause
日本語を話すことができます。	I can speak Japanese.	Plain form + ことができる
暇なとき、映画を見ます。	When I'm free, I watch movies.	Plain form + とき
安いから買った。	I bought it because it was cheap.	Plain form + から
行かないと言いました。	They said they wouldn't go.	Negative plain + と言う

Common Mistakes

Using ます form inside embedded clauses

• Wrong: おいしいですと思います。
• Right: おいしいと思います。
• Why: Before と思う, と言う, and similar structures, the clause must be in plain form. ます/です forms cannot be used here (except in very polite reported speech).

Forgetting だ with な-adjectives and nouns before certain structures

• Wrong: 静かと思います。
• Right: 静かだと思います。
• Why: な-adjectives and nouns need the copula だ in plain form before と (quotation). However, note that before か, だ is often dropped.

Mixing up casual speech and grammatical plain form

• Wrong: Thinking plain form is always "rude" or "male speech"
• Right: Plain form is grammatically necessary in many polite sentences (relative clauses, before と思います, etc.)
• Why: Even in polite speech, embedded clauses use plain form. The final verb determines the politeness level of the whole sentence.

Dropping だ when it should be there (and vice versa)

• Wrong: 学生だの？ (casual question)
• Right: 学生なの？
• Why: Before の (explanatory), だ changes to な for nouns and な-adjectives. This is a specific rule worth memorizing.

Usage Notes

In casual conversation between friends, plain form is the norm. Using ます form with close friends can sound distant or cold. However, many learners default to polite form for safety — this is fine until you build confidence with plain form.

Women and men both use plain form in casual settings. Historical claims that plain form is "masculine" are outdated. The sentence-final particles (よ, ね, わ) are what create gendered nuances, not the plain form itself.

When mixing politeness levels, the rule is: embedded clauses use plain form, and the final predicate determines the overall register. 昨日買った本はおもしろかったです is perfectly polite despite the plain form 買った inside the relative clause.

Practice Tips

• Convert your daily ます-form sentences to plain form and back. This builds fluency in both directions.
• Practice the four forms of each new verb you learn as a set: dictionary form, negative, past, past negative. Make it a habit.
• Start writing a casual diary in plain form. This gives you low-pressure practice without worrying about social appropriateness.

Related Concepts

• Prerequisite: Polite Form ます — the polite counterpart
• Next steps: ない-Form (Negative Plain) — detailed negative form rules
• Next steps: Relative Clauses — using plain form to modify nouns
• Next steps: Quotation Particle と — quoting with plain form
• Next steps: Ability ことができる — expressing ability with plain form
• Next steps: とき (when) — temporal clauses with plain form