Form Negative Sentences in Chinese: Subject + 不是 + Noun

To make a negative sentence out of a "S. + 是 + N." structure, simply put a 不 before 是. 



不 is a negative prefix meaning no or not. Let's take a look at the examples.

• 我不是小偷。(I'm not a thief.)

小偷 means thief. 小 means small. But 小 is sometimes used disapprovingly to suggest someone is low or base. 偷 means to steal.

• 你不是老闆。(you're not the boss. )

老闆 means boss. In simplified system, it's 老板. 老 means old. When 老 is used in a title, is shows respect or intimacy. 闆 originally means store or shop. 闆 is composed of two parts: 門 and 品. 門 means door. 品 means commodity. So,  the character 闆 suggests there are a lot product into/inside the door.

• 他們不是法國人。(They are not French people.)

法國means France. Add a 人 and it becomes 法國人, a French person or French people.

• 我們不是老師。(We are not teachers.)

老師 means teacher. 老 is the same with the 老 in 老闆. 師 means teacher or expert. Like many words in modern Chinese, 師 doesn't stand alone. It has to be combined with other words. If I want to say "I'm a teacher," I can't say “我是師.” I have to say “我是老師.”