助动词：应该

应该 is an auxiliary verb placed before the main verb. It expresses advice, responsibility, moral duty, social expectation, or a logical guess about what is right. It is softer than 必须 (“must”), but stronger and more serious than a casual suggestion.

Use 应该 to give advice: 你应该多休息. Use it to talk about proper behavior: 我们应该帮助别人. Use it for a reasonable expectation: 她现在应该在家.

The negative form is 不应该, meaning “should not.” It is usually used to point out inappropriate behavior or a bad choice: 你不应该对妈妈说谎. Do not say 应该不 for this meaning.

Compare 应该, 必须, and 要: 应该 means “should” based on what is right or reasonable; 必须 means “must” because there is a rule or strong requirement; 要 can mean “want / need / be going to.” If the action is required with no choice, 必须 is stronger. If it is advice, 应该 is more natural.

Word order is fixed: Subject + 应该 + Verb. Do not put 应该 after the verb or at the end of the sentence.