if是什么意思

You use if in conditional sentences to introduce the circumstances in which an event or situation might happen, might be happening, or might have happened.

You use if in indirect questions where the answer is either 'yes' or 'no'.

You use if to suggest that something might be slightly different from what you are stating in the main part of the sentence, for example that there might be slightly more or less of a particular quality.

You use if, usually with 'can', 'could', 'may', or 'might', at a point in a conversation when you are politely trying to make a point, change the subject, or interrupt another speaker.

You use if at or near the beginning of a clause when politely asking someone to do something.

You use if to introduce a subordinate clause in which you admit a fact which you regard as less important than the statement in the main clause.

You use if not in front of a word or phrase to indicate that your statement does not apply to that word or phrase, but to something closely related to it that you also mention.

You use if ever with past tenses when you are introducing a description of a person or thing, to emphasize how appropriate it is.

You use if only with past tenses to introduce what you think is a fairly good reason for doing something, although you realize it may not be a very good one.

You use if only to express a wish or desire, especially one that cannot be fulfilled.

You use as if when you are making a judgment about something that you see or notice. Your belief or impression might be correct, or it might be wrong.

You use as if to describe something or someone by comparing them with another thing or person.

You use as if to emphasize that something is not true.

You use 'if anything' to introduce something which strengthens or changes the meaning of the statement you have just made, but only in a small or unimportant way.

You use 'It's not as if' to introduce a statement which, if it were true, might explain something puzzling, although in fact it is not true.

You say 'if I were you' to someone when you are giving them advice.