Infinitives ② — Adjectival and Adverbial Usage

An infinitive can modify a noun like an adjective or modify a verb or adjective like an adverb. Let’s master all three usages studied in middle school.

Basic Rules

Adjectival usage is translated as “for doing” or “to do” and modifies the noun immediately before it (something to eat = something to eat). Adverbial usage has the following three meanings: ① purpose, “in order to do” (I came here to see you.) ② cause, “because...” (I am glad to meet you.) ③ result, “and then...” (He grew up to be a singer. = He grew up and became a singer).
The key is to determine the meaning from the relationship with the noun, verb, or adjective being modified.

Points to Note

① In adjectival usage, a preposition may be needed after the infinitive: a chair to sit on, a pen to write with, a friend to talk to / with. Check whether the original expression contains a preposition, as in “sit on a chair” and “write with a pen.”
② When emphasizing purpose in adverbial usage, “in order to” and “so as to” can also be used. “I came here in order to see you.” makes the purpose clear.
③ Adverbial usage expressing cause often follows an adjective: be glad / happy / sorry / sad / surprised + to do.
④ The logical subject of an infinitive: for + person + to do. It can show who something is difficult or easy for, as in “It is difficult for me to swim.”

Practice

1. Write “He has no friend to talk to” in English (using friend to talk to).
2. Write “I bought this book to study mathematics” in English.
3. Write “I am happy to meet her” in English.