A + 是 + B

'是' (shì) sentences — A is B

是 (shì, 'to be') links two nouns to say A is B — for identity, names, nationality, or category. Unlike English, Chinese doesn't conjugate 是 for tense or person, and adjectives never take 是 (那本书是新的 is wrong for 'that book is new' — use 是...的 or drop 是 entirely, see the 的 point). Negate with 不是, and ask yes/no questions by adding 吗 at the end.

Examples

我是老师。
wǒ shì lǎo shī
I am a teacher.
他是我朋友。
tā shì wǒ péng you
He is my friend.
这是我的猫。
zhè shì wǒ de māo
This is my cat.

Common mistake

✗ Wrong: 我是很忙。

✓ Right: 我很忙。

是 links two nouns, not a subject and an adjective. To describe how someone/something is, drop 是 and use an adverb like 很 before the adjective instead: 我很忙 (I am busy), not 我是很忙.

Practice this pattern

Fill in the missing character:

我＿老师。

I am a teacher.