if

1.如果；假若；倘若used to say that one thing can, will or might happen or be true, depending on another thing happening or being true

2.当；无论何时；每次when; whenever; every time

3.（与 will 或 would 连用，表示客气地请求）used withwill orwould to ask sb politely to do sth

4.（用于 ask、know、find out、wonder 等之后，引出两个或以上的可能性之一）是否used afterask ,know ,find out ,wonder , etc. to introduce one of two or more possibilities

5.（用于表示情感的动词或形容词之后）used after verbs or adjectives expressing feelings

6.（承认某事可能，但不很重要）即使，虽然used to admit that sth is possible, but to say that it is not very important

7.（置于形容词之前，引出对比）虽然，尽管used before an adjective to introduce a contrast

8.（请对方听自己的意见）used to ask sb to listen to your opinion

9.（置于 could、may 或 might 之前，提出建议或客气地打断别人的话）used beforecould ,may ormight to suggest sth or to interrupt sb politely

if and when

（谈及可能发生或不发生的事时说）used to say sth about an event that may or may not happen

if anything

（表达看法，或用在否定句之后表示反面意见才对）used to express an opinion about sth, or after a negative statement to suggest that the opposite is true

if I were you

（提出劝告时说）used to give sb advice

if not

（用在 if 引导的句子之后）不然，要不used to introduce a different suggestion, after a sentence withif

if only

但愿used to say that you wish sth was true or that sth had happened

its not as if

（表示所发生的事情令人惊讶）used to say that sth that is happening is surprising

only if

只有used to state the only situation in which sth can happen

1.(informal)不确定的情况a situation that is not certain

1.倘若,如果

2.〈口〉是否,是不是

3.要是,假设

4.虽然,即使

5....的时候总是...,一...就

6.要是...多好

1.条件,设想

1.used for introducing a situation that may happen or may be real, especially when talking about its results; used for introducing a situation or condition that must exist before something else happens; used for introducing a situation that does not exist now and is unlikely or impossible, especially when talking about its imaginary results; used for introducing a situation that might have existed in the past but did not exist, especially when talking about what its results might have been

2.used for introducing a situation that always has the same result, meaning, or effect

3.used in indirect questions that ask whether something is true; used when talking about something that is not certain

4.used for introducing the reason that you think someone may want to know something

5.used for saying how you feel about the possibility that something may happen or be true; used when expressing an opinion about an imagined situation

6.used when politely asking someone to do something or when asking for permission to do something; used when politely trying to add something to a conversation or discussion

7.used for introducing a remark that makes your description seem slightly less positive or certain

8.used for referring to something that someone may have noticed, before explaining the reason for it

9.used for suggesting that something may possibly be more or less, better or worse, etc. than you have stated

10.used for introducing a negative expression to emphasize that you think something is very surprising or shocking