if
conj. 如果, 是否, 无论何时, 假设, 即使 n. 条件 [计] DOS批处理命令:根据所测试的条件决定是否执行另一条命令
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词形变化
别名
教材释义与例句
条件；设想
used when saying what someone's feelings are about a possible situation
（表条件）如果；即使；是否；（表假设）假如
used when talking about something that might happen or be true, or might have happened
释义与例句
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1.
An uncertainty, possibility, condition, doubt etc.
非正式The board can't approve this project; there are too many ifs.
1709, Susannah Centlivre, The Busy Body, Act III, in John Bell (ed.), British Theater, J. Bell (1791), page 59, Sir Fran. Nay, but Chargy, if——— ¶ Miran. Nay, Gardy, no Ifs.——Have I refus'd three northern lords, two British peers, and half a score knights, to have put in your Ifs?
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1.
Supposing that, assuming that, in the circumstances that; used to introduce a condition that may be (or prove to be) either true or false.
If crossing the road, make sure you look both ways.
If I give you the money would/will you buy it for me?
If you prefer, I can come tomorrow instead.
I'll, if I have time, do it next week.
I'll come only if you will do the driving.
Fetch me a cold beer if there's one in the fridge.
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2.
Supposing that, assuming that, in the circumstances that; used to introduce a condition that may be (or prove to be) either true or false.
A keyword that invokes conditional processing: in the event that a given condition is true, execute the given statement(s) (otherwise execute other statements).
计算机 工程 数学if A then B else C
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3.
Supposing that; used with past or past perfect subjunctive to indicate a counterfactual or hypothetical condition.
If she hadn't told me, I wouldn't know.
"You would be healthier if you would give up smoking" "Well, if I were rich, I'd go to one of those hypnosis therapies to quit".
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4.
Supposing that; used with past or past perfect subjunctive to indicate a counterfactual or hypothetical condition.
Even if; even in the circumstances that.
I wouldn't marry you if you were the last man on earth.
You're finishing your chowder if you sit there all afernoon!
If it’s the last thing I do / If it takes me from Tubilo to Timbuktu / If it’s the last thing I do / I’m gonna dodge every road block, speed trap, county cop / To get my hands on you / If it’s the last thing I do.
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5.
Considering the fact that; given that; introducing a condition that is known to be true.
The drain's blocked — and if the drain's blocked, the water won't flow.
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6.
When; whenever; every time that.
If you heat water to 100° C, it boils.
If it rains, it pours.
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7.
Although; used to introduce a concession; may..but.
He was a great friend, if a little stingy at the bar.
She won her team's admiration, if not the award, for her performance.
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8.
Whether; used to introduce a noun clause, an indirect question, that functions as the direct object of certain verbs.
是否
I don't know if I want to go or not.
Quoth Matthew, “ […] / She doubts if two and two make four, / […] ”
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9.
Introducing a relevance conditional; in case.
I have leftover cake if you want some.
If you want to go home, I have the car keys.
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10.
While; used to introduce a contrast.
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相关短语
词源
From Middle English if, yif, yef, from Old English ġif (“if”), from Proto-West Germanic *jabu, *jabē, from Proto-Germanic *jabai (“when, if”). Cognate with Scots gif (“if, whether”), Saterland Frisian af, of (“if, whether”), West Frisian oft (“whether”), Dutch of (“or, whether, but”), Middle Low German ef, if, af, of ("if; whether"; > German Low German of), German ob (“if, whether”), Icelandic ef (“if”).
来源：wiktionary