Japanese Past Tense: ました, た-form, and でした
Mastering the past tense is a huge milestone in your Japanese journey. It unlocks the ability to share stories, talk about your weekend, and describe historical events. Japanese has two main past tense forms: the polite ました for formal situations, and the plain た-form for casual conversation and subordinate clauses. This guide will walk you through all the conjugation rules, from verbs to adjectives to nouns, with plenty of examples to get you speaking about the past with confidence.
The Polite Past Tense: ～ました
The polite past tense is your go-to for conversations with people you don't know well, in professional settings, or when you want to show respect. It's formed by taking the polite present tense form (ます) and changing it to ました.
昨日、勉強しました。
Kinō, benkyō shimashita.
I studied yesterday.
本を読みました。
Hon o yomimashita.
I read a book.
The Plain Past Tense: た-form
The plain past tense, or た-form, is used in casual conversation with friends and family. More importantly, it's essential for forming complex sentences and relative clauses (e.g., "the book that I read"). Conjugating to the た-form follows similar rules to the て-form.
た-form Conjugation Rules
| Verb Group | Dictionary Form | た-form | Rule |
|---|---|---|---|
| Group 1 (う-verbs) | 行く (iku) | 行った (itta) | く → いた |
| Group 1 | 泳ぐ (oyogu) | 泳いだ (oyoida) | ぐ → いだ |
| Group 1 | 待つ (matsu) | 待った (matta) | つ → った |
| Group 1 | 死ぬ (shinu) | 死んだ (shinda) | ぬ → んだ |
| Group 1 | 遊ぶ (asobu) | 遊んだ (asonda) | ぶ → んだ |
| Group 1 | 飲む (nomu) | 飲んだ (nonda) | む → んだ |
| Group 1 | 帰る (kaeru) | 帰った (kaetta) | る → った |
| Group 2 (る-verbs) | 食べる (taberu) | 食べた (tabeta) | る → た |
| Irregular | する (suru) | した (shita) | Memorize |
| Irregular | 来る (kuru) | 来た (kita) | Memorize |
Tip: The conjugation rules for た-form are identical to those for the て-form, except you replace て/で with た/だ. If you know one, you know the other!
友達に会った。
Tomodachi ni atta.
I met a friend.
映画を見た。
Eiga o mita.
I watched a movie.
Negative Past Tense
To say that you didn't do something in the past, you use the negative past tense. The conjugation is the same for both polite and plain styles, you just change the ending of the negative present form.
- Polite Negative Past: ません → ませんでした
- Plain Negative Past: ない → なかった
勉強しませんでした。 (Polite)
Benkyō shimasen deshita.
I did not study.
勉強しなかった。 (Plain)
Benkyō shinakatta.
I did not study.
Past Tense of い-Adjectives
To put い-adjectives in the past tense, you replace the final い with かった for both affirmative and negative forms. There is no separate polite/plain distinction for adjectives themselves; the politeness is determined by the sentence-ending copula (です or its absence).
- Affirmative: 高い (takai) → 高かった (takakatta)
- Negative: 高くない (takakunai) → 高くなかった (takakunakatta)
昨日は寒かったです。 (Polite)
Kinō wa samukatta desu.
It was cold yesterday.
パーティーは楽しかった。 (Plain)
Pātī wa tanoshikatta.
The party was fun.
Warning: The one common exception is the adjective いい (ii, good). Its past tense is not いかった but よかった (yokatta), which comes from its alternative form よい (yoi).
Past Tense of な-Adjectives and Nouns
For nouns and な-adjectives, the past tense is formed using the copula だ (plain) or です (polite).
- Polite Affirmative Past: Noun/な-Adjective + でした
- Polite Negative Past: Noun/な-Adjective + じゃありませんでした or ではありませんでした
- Plain Affirmative Past: Noun/な-Adjective + だった
- Plain Negative Past: Noun/な-Adjective + じゃなかった or ではなかった
彼は先生でした。 (Polite)
Kare wa sensei deshita.
He was a teacher.
その部屋は静かだった。 (Plain)
Sono heya wa shizuka datta.
That room was quiet.
Practice
Conjugate the following into the polite past affirmative, plain past affirmative, and plain past negative.
- 書く (kaku - to write)
- 元気 (genki - healthy)
- 高い (takai - expensive)
- 見る (miru - to see)
Answers: 1. 書きました, 書いた, 書かなかった | 2. 元気でした, 元気だった, 元気じゃなかった | 3. 高かったです, 高かった, 高くなかった | 4. 見ました, 見た, 見なかった
Key Takeaways
- Use ました for polite past tense verbs and た-form for plain past tense verbs.
- The た-form conjugation rules are identical to the て-form rules.
- For negative past, change ません to ませんでした (polite) and ない to なかった (plain).
- い-Adjectives become past tense by changing い to かった.
- Nouns and な-adjectives use the copula: でした (polite affirmative) or だった (plain affirmative).
- Remember the exception: いい becomes よかった.
With these rules. Keep practicing by writing short diary entries about your day!