Page 294 - Practical English Usage 3ed - Michael Swan, Oxford

infinitives (8): who to ..., what to ... etc 286
5 infinitive with preposition: a friend to play with
A noun can be followed by infinitive + preposition. Mary needs a friend to play with.
He's looking for a flat to live in.
In a very formal style, another structure is possible: noun + preposition + whom/which + infinitive.
Mary needs a friend with whom to play.
He's looking for a place in which to live.
This is not possible when there is no preposition. One cannot say, for example, .. lleeti a b66k which ttl read.
6 the life to come etc
In expressions like the life to come (= life after death), the world to come, his wife to be (= his future wife), the infinitive has a future meaning, and is similar to a relative clause with be (= the life/world that is to come, etc.)
For infinitives used to talk about people's purposes, see 289.
For passive infinitives (e.g. There's lUork to be done.), see 287.
For for + object + infinitive (e.g. Is tllere any IJeeil for us to stay?), see 291.5.
For infinitives after first, next, Inst or superlative + noun (e.g. the first looman to climb Everest),
see 284.3.
For more about structures with prepositions at the end, see 452.
286 infinitives (8): who to ... , what to ... etc
1 indirect questions: Tell us what to do
In indirect speech (see 277.2), we can use an infinitive after the question words who, what, where etc (but not usually why). This structure expresses ideas such as obligation and possibility.
I wonder who to invite. (= .•. who I should invite.)
Tell us what to do.
Gan you show me how to get to the station? (= ... how I can get to the
station?)
I don't know where to put the car. Tell me when to pay. I can't decide whether to answer her letter.
(BUT NOT I can't ttntlersttmtl wlty ttl tI6 it.)
2 direct questions: What shall we do?
We do not usually begin a direct question with How to ...?, What to ...?etc. After question words, we often use shall and should.
How shall I tell her? (NOT H"(Jw ttl tell Iter?) What shall we do? (NOT Ylhat ttl tI6?)
Who should I pay? (NOT Yi'h6 ttl !'tty?)
3 titles
How to ..., What to ... etc are often found as titles for instructions, information leaflets, books etc. (Note: these are not questions.)
HOW TO IMPROVE YOUR PRONUNCIATION WHAT TO DO IF FIRE BREAKS OUT
For questions beginning Why (not) + infinitive, see 628.
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