Modal Verbs: Modal verbs are a type of auxiliary that express necessity, possibility, permission, or ability, such as 'can', 'may', 'must', and 'should'.
Perfect Aspect: The perfect aspect is a grammatical construction that describes completed actions and is formed using auxiliary verbs like 'have' followed by the past participle of the main verb.
Passive Voice: Passive voice is a grammatical construction where the subject receives the action of the verb, typically formed with the auxiliary verb 'be' followed by the past participle of the main verb.