Question re: proper usage of to + infinitive construction
- My mother bought the book for me to study English
The sentence as printed is indeed ambiguous, like all written sentences. But, also like almost all written sentences, it's not ambiguous when it's spoken, since the stress and intonation are different in the different senses.
One meaning would be something like
- My mother bought the book so that I could study English.
Here the purpose of the book is clear, and the intended student is identified as the speaker, though the end possessor of the book is not identified. Since buy is not a bitransitive verb, for me can't be an indirect object, so we are left to infer that the speaker is now the owner of the book.
On this reading, the prepositional phrase for me would get the primary stress, as befits a marked subject of a purpose clause:
- My mother bought the book for me to study English
Another meaning might be something like
- My mother bought me the book, to study English.
Here it's not clear who's studying English, but it is clear that the book changed possession; even though buy is not bitransitive, it can undergo Dative under certain conditions which are met here. One could infer that the speaker would be the one studying English with my new book, but that's not what it says; it's possible my mother is intending to study.
On this reading, the noun phrase the book would receive primary stress:
- My mother bought the book for me to study English
There are also differences in the pitch accent of different words in these sentences that I can't go into in print. Suffice it to say that
- There is more than one meaning for this sentence,
because there is more than one pronunciation. - The meanings of this sentence, while different, are not that different;
they can all describe the same event, for instance.
This situation is true for more than one sentence in English; in fact, it is the norm to be ambiguous,
and for the different senses to be so similar in context that we don't even notice.