GrammarJLPT N5
→ was
Past Tense of the Copula (was / were)
JLPT N5CopulaNeutral
だった and でした are the past tense forms of the Japanese copula (the equivalent of "to be"). They are used to state that something was or were something in the past, linking a subject to a noun or a な-adjective that applied at a previous time. だった is the casual past form of だ, while でした is the polite past form of です. Both carry the same core meaning — "was" or "were" — but differ in formality. You use だった when speaking informally with friends or family, and でした in polite conversation, business settings, or when speaking to someone you are not close to. These forms attach directly after nouns and な-adjective stems (without な). It is important to distinguish them from the past tense of い-adjectives, which do not use だった or でした but instead conjugate by changing い to かった (casual) or かったです (polite).
Examples
Example #1
きのうは 休みだった。
Here the noun 休み (day off) is linked to the subject きのう (yesterday) using the casual past copula だった. This is a straightforward statement about what yesterday was. Because だった is casual, this would be used among friends or in informal writing such as a diary.Yesterday was a day off.
Structures
- Noun
- Noun + だった (casual) / でした (polite)
- な-Adjective
- な-Adjective stem + だった (casual) / でした (polite)
Common mistakes
A very common mistake is using だった or でした with い-adjectives. For example, saying 「おいしいだった」 is incorrect; the correct casual past is おいしかった and the polite past is おいしかったです. Another frequent error is mixing register by using だった in a polite context or でした in a very casual one, which can sound awkward or out of place. Beginners also sometimes forget to drop な from な-adjectives before attaching the copula, producing incorrect forms like 「きれいなだった」 instead of the correct 「きれいだった」. Finally, some learners confuse でした with the negative past じゃなかった / ではありませんでした; remember that でした is the affirmative past ("was"), not the negative.
Related
だですではないじゃなかった・ではありませんでしただろう・でしょう