Negation: Add not after the be verb (often contracted).
他He 不是is not 一名a 老师teacher.
He is not a teacher. (= He isn't a teacher.)
Interrogative: Place the be verb before the subject.
(是吗)Are 你you 准备好ready?
Are you ready?
Short answers: Yes, I am. / No, I'm not.
Note: Negative contractions: is not → isn't, are not → aren't; but am not is only contracted to I'm not (there is no ~~amn't~~).
Common Errors
- ❌ ~~He busy.~~ → ✓ He is busy. — In Chinese, "He is very busy" can exist without a verb, but an English sentence must have a verb. Use be to link when the predicative is an adjective or noun and there are no other verbs in the sentence (He is busy); do not add be if the sentence already contains an ordinary verb (I go to school).
- ❌ ~~I am go to school.~~ → ✓ I go to school. — Do not use be and ordinary verbs together; "go" alone suffices for "to go."
- ❌ ~~They is my friends.~~ → ✓ They are my friends. — Plural subjects (you / we / they) take are.
- ❌ ~~I am agree.~~ → ✓ I agree. — agree is itself a verb; do not add am before it.
- ❌ ~~Are you ready? — Yes, I'm.~~ → ✓ Yes, I am. — Contractions cannot be used at the end of affirmative short answers (say Yes, I am); however, negative short answers typically end with a negative contraction (No, he isn't / No, I can't; first person is No, I'm not, as there is no amn't).