English as a Second Language/Infinitives



How can someone determine whether on not an infinitive is functioning as an adjective?

Here are three sentences with infinitives:

1. He gave her a book to read.

2. He gave a book for her to read.

3. It is relaxing for her to read a book.

In 1. does "to read" function as an adjective modifying "book"?

In 2. does "to read" function as an adjective modifying "her"?

In 3. does "to read" a book function as an adjective modifying "her"?

I thank you for your reply.

Hi Kenneth,

Interesting question.

Adjectives modify nouns and usually answer questions like: "What kind?" or "Which?" or "How many?" With that in mind, I'd say "to read" is an adjective only in the first of the three sentences you've asked about.

See if the following links help.





Also the "substitution test" might be a useful tool here. If a word or phrase can substitute a word or phrase in a sentence; that is, the sentence is grammatical with the substitute, then the substitute has the same or similar function to the word substituted in that sentence. Sometimes, we cannot substitute a word or expression in the same place in the sentence as another word or expression, although the substitutions are nonetheless equivalent. For instance, see adjectives, where an adjective usually precedes a headword, but an adjectival phrase follows it. Also, it may be necessary to change the person of the verb.

Back to your examples:

1. He gave her a book to read = He gave her a big book (big is an adjective, and so is "to read")

2. He gave a book for her to read - He gave a book for her big ... this doesn't make sense.

3. It's relaxing for her to read a book - It's relaxing for her big a book ... again this doesn't make sense

So "to read" is an adjective in the first but not in the second or the third of your sentences.


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Amy Baker


I can answer question about grammar, spelling, syntax, idioms, reading and/or writing that pertain to English as a Second Language. I am knowledgeable about both TOEFL and IELTS.


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