Prepositions show the relationships between nouns or pronouns and other words: about, above, after, against, among, before, between, by,
during, for, from, in, on, over, through, till, to, under, until, with.
In formal English, the traditional rule of use was that clauses and sentences should not end with prepositions. Preposition should instead be
positioned before their objects (hence the name preposition), often the relative pronouns which and whom –
She is the only friend I can confide in. (Informal)
She is the only friend in whom I can confide. (Formal)
He was not the easiest man to relax with. (Informal)
He was not the easiest man with whom to relax. (Formal)
This is something we can learn a great deal from. (Informal)
This is something from which we can learn a great deal. (Formal)
Sleep is a phenomenon we still know very little about. (Informal)
Sleep is a phenomenon about which we still know very little. (Formal)
But authorities agree that there is no grammatical justification for this rule. Just like the rule forbidding the split infinitive, it is grounded on
nothing more than an attempt to imitate Latin. Besides, its consistent application would result in some very odd constructions –
It was not a pleasant experience through which to go.
There was nothing more about which to talk.
In some cases, the results would be barely intelligible –
For what is it?
Hence Sir Winston Churchill’s apocryphal parody of the rule: This is the sort of English up with which I will not put.
At any rate, the rule is relaxing. A modern job applicant is just as likely to write the post I am applying for as the post for which I am applying.
And the rule should certainly be ignored where it would ruin eloquence –
‘A faith is something you die for; a doctrine is something you kill for.
There is all the difference in the world.’
1 Tony Benn, BBC TV, 11 April 1989