the to-infinitive = to + base (to sit)
the zero infinitive = base (sit)
Functions of the to-infinitive:
- To indicate the purpose or intention of an action. eg: She came to collect her pay cheque.
- As the subject of the sentence: eg: To visit the Grand Canyon is my life-long dream.
- To indicate what something can or will be used for: eg: I don't have anything to wear.
- After adjectives: subject + to be + adjective + (for/of someone) + to-infinitive + (rest of sentence). eg: It is good to talk.
- To make a comment or judgement: Subject + to be + noun phrase + to-infinitive. eg: It was a stupid to place to stay.
- With adverbs. eg: I had too many books to carry.
- With question words: The verbs ask, decide, explain, forget, know, show, tell, & understand can be followed by a question word such as where, how, what, who, & when + the to-infinitive. eg: Do you understand what to do?
- After auxiliaries. eg: She can't speak to you.
- After verbs of perception. eg: We heard them close the door.
- After the verbs 'make' and 'let'. eg: Her parents let her stay out late.
- After the expression 'had better'. eg: We had better reserve a room in the hotel.
- with "why". eg: Why wait until tomorrow?
