I have learnt two points about "to-infinitive" as follows.

verb + to + infinitive

Its meaning is similar to "in order to" or "so as to".

  • I come to pick you up.
  • She runs to catch the bus.

adjective + to + infinitive

  • It is hard to learn many languages simultaneously.
  • This book is difficult to comprehend.


Does the structure "noun+to+infinitive" exist in English grammer? For example:

  • I lend a screwdriver to open your watch.
  • I am the math teacher to substitute for Mr. X who is absent today.

Bonus question: What is the difference (if any) between the following sentences?

A: This book is difficult to comprehend.

B: This book is difficult to be comprehended.

  • Sentence B is ungrammatical. Commented Dec 21, 2018 at 10:24
  • One of this site's rules is that a question here should focus on a single topic, so it's best not to ask "bonus questions". You should ask about "difficult to be comprehended" in a separate question.
    – TimR
    Commented Dec 21, 2018 at 11:37

2 Answers 2


Yes, that pattern with a noun is grammatical.

What's this?
-- It's a hat to put your beer in when you go to the football game.

Here's a screwdriver to open your watch with.

The construction indicates "intended purpose".

Your teacher example is not right if your desired meaning is "I am the substitute". Normally there'd be a participle clause there for that meaning, ...teacher substituting for ....

There's a prospective sense in this noun + infinitive construction:

We're going to make a presentation to Acme Widgets next week.
-- Joe's the man to take with you. He knows their product line very well.

Joe is suitable for the intended purpose, namely, making a presentation to Acme Widgets.

So your sentence about the substitute teacher would be valid in a discussion about who would be a suitable substitute teacher for Mr. X; you would be suggesting that you are a person suited to that job:

I don't know who we should send as the substitute teacher.
-- I'm just the math teacher to substitute for Mr. X, since I taught those students for most of last semester while Ms. J was out on maternity leave.


Yes it is used and your examples (especially the second one) is correct.

You should not think of the first example as a structure of its own ""noun + infinitive". It is a sentence with indirect object. The more clear way to express that would be something in the lines of: "I lent him a screwdriver to open..." for which the direct and indirect objects can switch places and a proposition would be necessary: "I lent a screwdriver to him to open..."

The bonus answer: The two sentences imply the same meaning and concept, however, the second way is not so commonly used since it is a passive sentence for a situation when passive would not be necessary, because the omitted subject is not known.

keep on learning and good luck, Travis

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