Why You Need This
You're reading a manga, watching anime, or looking at a dictionary. Everything is in plain form. But you need to speak politely to your teacher, a stranger, or at work. How do you go from 飲む to 飲みます on the fly?
This is one of the most practical skills in early Japanese. Converting plain form to ます form in your head without hesitation. Our lesson on formal and casual speech puts this conversion into practice with real dialogue.
The Conversion Process
Step 1: Identify the Verb Group
Before converting, you need to know which verb group the verb belongs to. Quick reminders:
- Ends in anything other than る? → U-verb (飲む, 書く, 話す, etc.)
- Ends in る with い/え sound before it? → Probably ru-verb (食べる, 見る)
- する or 来る? → Irregular
Step 2: Apply the Rule
U-verbs: Change the final う-row kana to its い-row equivalent, then add ます:
| Ending | Change | Example |
|---|---|---|
| う → い | う→い row | 買う → 買います |
| く → き | く→き | 書く → 書きます |
| ぐ → ぎ | ぐ→ぎ | 泳ぐ → 泳ぎます |
| す → し | す→し | 話す → 話します |
| つ → ち | つ→ち | 待つ → 待ちます |
| ぬ → に | ぬ→に | 死ぬ → 死にます |
| ぶ → び | ぶ→び | 遊ぶ → 遊びます |
| む → み | む→み | 読む → 読みます |
| る → り | る→り | 帰る → 帰ります |
Ru-verbs: Drop る, add ます:
| Plain | Polite |
|---|---|
| 食べる | 食べます |
| 見る | 見ます |
| 起きる | 起きます |
| 寝る | 寝ます |
| 着る | 着ます |
Irregulars:
| Plain | Polite |
|---|---|
| する | します |
| 来る (kuru) | きます |
The Reverse: Masu to Plain
Going the other direction is equally useful:
- Remove ます
- What's left is the verb stem
- For u-verbs: change い-row back to う-row
- For ru-verbs: add る back
飲みます → 飲み → 飲む
食べます → 食べ → 食べる
します → し → する