だって is a very common word in casual speech. When you hear it at the start of a sentence, it often means 'because' or 'but', and it carries a defensive or explanatory tone. For example, if someone scolds you for being late, you might say 'だって、電車が止まったんだ' (Because the train stopped). It can also be used to argue back, like 'but' – 'だって、知らなかったんだもん' (But I didn't know). In that use, it often sounds a bit childish or whiny, so be careful in polite situations.

As a particle, だって means 'even' or 'too', and it attaches to a noun or pronoun. For example, '私だってできる' means 'Even I can do it' or 'I can do it too', depending on context. It emphasizes that the speaker or the subject is included, often against expectations.

Note that there is a separate colloquial construction 〜たって (contracted from 〜ても) meaning 'even if', as in 'いくら言ったって' (no matter how much you say). This is not the same as the particle だって. In this entry, we focus on the 'because/but/even/too' uses.

だって is very colloquial, so it appears mostly in spoken Japanese or in dialogue in manga and novels. In formal writing or speech, use から, でも, 〜ても, or さえ instead.