Verb Stems (i-form) | Japanese Conjugation Base

What is the Verb Stem?

The verb stem (also called the i-form or masu-stem) is the most fundamental building block in Japanese conjugation. It's what you get when you strip ます off a polite verb. And it's the piece you attach ます, ません, ました, and ませんでした to.

But the stem does more than just build polite forms. It creates compound verbs, turns verbs into nouns, connects actions in formal writing, and pairs with helper verbs to add nuance.

How to Make the Stem

U-verbs (Group I)

Change the final う-row kana to its い-row equivalent:

Dictionary	Stem
行(い)く (iku)	行(い)き
書(か)く (kaku)	書(か)き
話(はな)す (hanasu)	話(はな)し
飲(の)む (nomu)	飲(の)み
待(ま)つ (matsu)	待(ま)ち
遊(あそ)ぶ (asobu)	遊(あそ)び
歌(うた)う (utau)	歌(うた)い
帰(かえ)る (kaeru)	帰(かえ)り

The shift: う→い, く→き, す→し, つ→ち, ぬ→に, ぶ→び, む→み, る→り.

Ru-verbs (Group II)

Just drop the る:

Dictionary	Stem
食(た)べる (taberu)	食(た)べ
見(み)る (miru)	見
起(お)きる (okiru)	起(お)き
覚(おぼ)える (oboeru)	覚(おぼ)え

Irregular Verbs

Dictionary	Stem
する	し
来(く)る (kuru)	き

The Shortcut

If you already know a verb's masu-form, the stem is just what's left after removing ます:

Masu-Form	Stem
行(い)きます	行(い)き
食(た)べます	食(た)べ
します	し

This is why it's often called the "masu-stem."

Uses of the Verb Stem

1. Building Polite Forms

Stem + ます/ません/ました/ませんでした:

飲(の)み + ます = 飲(の)みます

2. Compound Verbs

Stem + another verb creates compound verbs with combined meanings:

食(た)べ + 始(はじ)める = 食(た)べ始(はじ)める (start eating)
読(よ)み + 終(お)わる = 読(よ)み終(お)わる (finish reading)
走(はし)り + 出(だ)す = 走(はし)り出(だ)す (break into a run)

3. Noun-ification

Many stems function as nouns:

飲(の)み = a drink (飲(の)み会 = drinking party)
帰(かえ)り = the way back (帰(かえ)りに = on the way back)
休み = a break/holiday

4. Formal Sentence Linking

In written or formal Japanese, stems can link clauses (like a formal version of te-form):

朝(あさ)起(お)き、顔(かお)を洗(あら)い、出かけた (woke up, washed my face, and left)

Example Sentences

食(た)べ始(はじ)めましょう。 (tabe hajimemashou.) — Let's start eating.
帰(かえ)りに買(か)い物(もの)した。 (kaeri ni kaimono shita.) — I went shopping on the way home.
読(よ)み終(お)わった？ (yomi owatta?) — Did you finish reading?
一曲(いっきょく)歌(うた)いたいです。 (ikkyoku utaitai desu.) — I'd like to sing a song.
お昼(ひる)何(なに)食(た)べたい？ (ohiru nani tabetai?) — What do you want to eat for lunch?
走(はし)り出(だ)した。 (hashiridashita.) — He broke into a run.
飲(の)み会に行(い)く？ (nomikai ni iku?) — Are you going to the drinking party?
彼(かれ)は覚(おぼ)えが早(はや)い。 (kare wa oboe ga hayai.) — He learns fast.