What's the main difference between "hasn't" and "haven't"? And how could I know which is the correct one for the context?

Native speaker’s answer
Rebecca
Great question! "Has" is used with the pronouns he, she, it, and singular nouns. "Have" is used with the pronouns: I, you, we, they, and group nouns. The same applies for the contractions <hasn't> and <haven't>, as they are negative forms of "has" and "have". Ex: I haven't seen that movie before. Ex: She hasn't seen that movie before. Ex: They haven't eaten dinner. Ex: He hasn't eaten dinner. Ex: My students haven't written their test yet. Ex: My student, Peter, hasn't written his test yet. Ex: It hasn't snowed this winter.