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 |
|---|---|
| 行く (iku) | 行き |
| 書く (kaku) | 書き |
| 話す (hanasu) | 話し |
| 飲む (nomu) | 飲み |
| 待つ (matsu) | 待ち |
| 遊ぶ (asobu) | 遊び |
| 歌う (utau) | 歌い |
| 帰る (kaeru) | 帰り |
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 |
|---|---|
| 食べる (taberu) | 食べ |
| 見る (miru) | 見 |
| 起きる (okiru) | 起き |
| 覚える (oboeru) | 覚え |
Irregular Verbs
| Dictionary | Stem |
|---|---|
| する | し |
| 来る (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 |
|---|---|
| 行きます | 行き |
| 食べます | 食べ |
| 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:
- 飲み + ます = 飲みます
2. Compound Verbs
Stem + another verb creates compound verbs with combined meanings:
- 食べ + 始める = 食べ始める (start eating)
- 読み + 終わる = 読み終わる (finish reading)
- 走り + 出す = 走り出す (break into a run)
3. Noun-ification
Many stems function as nouns:
- 飲み = a drink (飲み会 = drinking party)
- 帰り = the way back (帰りに = 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):
- 朝起き、顔を洗い、出かけた (woke up, washed my face, and left)