だ

To be, Is

アイスクリームだ。

It is ice cream.

Explanation

「だ」 means 'is / am / are' when you are not being polite: with friends and family, or in writing. It means the same as 「です」, just less formal. In casual questions people drop it and raise their voice: 「学生？」

Mixed up with

「です」 is polite (for teachers, bosses, strangers); 「だ」 is casual (friends, family).

Never put 「だ」 after an い-adjective: not 「高いだ」, just 「高い」, or 「高いです」 to be polite.

Examples

お寺てらだ。
It is a temple.
大おおきい家いえだ。
It is a big house.
私わたしだ。
It is me.
危険きけんだ。
It is dangerous.
大切たいせつだ。
It is important.
本ほんだ。
It is a book.
猫ねこだ。
(It) is a cat.
学生がくせいだ。
(I) am a student.
綺麗きれいだ。
It is beautiful.
海うみだ。
It is the sea.
映画えいがだ。
It is a movie.
好すきだ。
I like it.
家いえだ。
It is a house.
水みずだ。
It is water.
同おなじだ。
It is the same.
大変たいへんだ。
It is terrible.
質問しつもんだ。
It is a question.