B：Sounds (nice/ exciting/ thrilling).
      听起来（不错/很刺激/惊险）。

A：You’re welcome to join me if you want.
      如果你愿意欢迎你加入我们。

A：Do you mind if I ask you a favor?
      我可以请您帮个忙吗?

B：No, not at all.
      没问题，完全可以。

A：Is this seat empty?
      这个座位是空的吧？

if

B：Yes, and this one will be if you sit down.
      是的，如果你坐下，我的座位就是空的。

1. (表示条件或假设)假如，如果，要是
    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.

if什么意思

    e.g. She gets very upset if I exclude her from anything...
           要是有什么事情我不让她参加,她会非常难过。
    e.g. You'll feel a lot better about yourself if you work on solutions to your upsetting situations...
           如果你设法找到解决自己麻烦的办法,你自我感觉会好得多。

2. (用于间接疑问句)是否
    You use if in indirect questions where the answer is either 'yes' or 'no'.

    e.g. He asked if I had left with you, and I said no...
           他问我是否和你一块儿离开的,我说不是。
    e.g. I wonder if I might have a word with Mr Abbot?
           请问我能否和阿博特先生说几句话？

3. (表示与句子主要部分的陈述稍有不同)即便，纵然，虽然
    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.

    e.g. Sometimes, that standard is quite difficult, if not impossible, to achieve...
           有时即便有可能达到那个标准，那也是非常困难。
    e.g. I'm working on my fitness and I will be ready in a couple of weeks, if not sooner...
           我正在调养身体,最多两三周以后就可以了。

4. 如果…可以的话(通常与can，could, may 或 might 连用,在谈话中礼貌地提出自己的观点、转换话题或打断对方)
    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.

    e.g. If I could just make another small point about the weightlifters in the Olympics...
           请允许我就有关奥运会举重运动员的问题再补充一点。
    e.g. So, if we may return strictly to athletics again for a few minutes...
           因此,如果我们可以再花几分钟重新回到田径运动话题上来的话……

5. (用于句首，表示礼貌地请求某人做某事)
    You use if at or near the beginning of a clause when politely asking someone to do something.

    e.g. I wonder if you'd be kind enough to give us some information, please?
           请问您能不能给我们提供一些信息？
    e.g. If you will just sign here, we will arrange for your bank to deduct your payments automatically.
           麻烦您在这里签一下字,我们将联系您的银行自动扣除您的付款。

6. (用于引导从句中较次要的事实)即便
    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.

    e.g. If there was any disappointment it was probably temporary...
           即便有点儿失望,也肯定是暂时的。
    e.g. Even if I'm overstating the case for nutrition, at least it will result in the woman being in charge of her own symptoms...
           即便我夸大了营养的重要性,但至少它会让这个女人知道关注自己的症状。

7. 要是不;即使不
    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.

if的反义词

    e.g. A number of recent advances hold out if not the hope of a cure, then at least the possibility of some drug which could stop the spread of the virus...
           近来的一些进展即使不能提供治愈的希望,也至少有望研制出来某种药物来阻止病毒的传播。
    e.g. She understood his meaning, if not his words, and took his advice.
           她即便没听懂他的话,也明白了他的意思,并且接受了他的建议。

8. (用于过去时,加强语气)如果真的…
    You use if ever with past tenses when you are introducing a description of a person or thing, to emphasize how appropriate it is.

    e.g. I became a distraught, worried mother, a useless role if ever there was one...
           我变成了一个忧心如焚的母亲,一个全无用处的角色。
    e.g. If ever there was the right person in the right job it was she...
           要是真的有才尽其用的人,那就是她。

9. (与过去时连用，引出一个相对合理的理由)即使仅仅为了(或因为)…
    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.

    e.g. She writes me often, if only to scold me because I haven't written to her...
           她常来信,即使仅仅为了责怪我还没回信给她。
    e.g. A one-to-one meeting with the US President was necessary, if only for a deeper exchange of views.
           与美国总统一对一的会谈是必要的,即便仅仅是为了双方观点更深入的交流。

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

      e.g. If only you had told me that some time ago...
             要是你早些时候告诉我该多好啊！
      e.g. If only it were that simple!...
             要是那么简单就好了！

11. (表示判断)好像,仿佛,似乎
      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.

      e.g. The whole room looks as if it has been lovingly put together over the years...
             整个房间看起来好像是经过了多年的精心布置。
      e.g. His heart was pounding, as if he were frightened.
             他的心怦怦跳,似乎被吓坏了。

12. (表示类比)好像，仿佛，似乎
      You use as if to describe something or someone by comparing them with another thing or person.

      e.g. He points two fingers at his head, as if he were holding a gun...
             他把两根手指指向他的头,仿佛他正举着一支枪。
      e.g. The two cousins looked as if they'd been carved from blocks of ice.
             两个堂姊妹看起来像由冰块雕刻而成。

13. (强调某物不是真的)好像…一样,仿佛,似乎
      You use as if to emphasize that something is not true.

      e.g. My husband, for some unknown reason, suggested that I loved my birds more than him: as if I would...
             我丈夫,莫名其妙地,暗示我爱鸟甚于爱他：仿佛我真如此似的。
      e.g. Getting my work done! My God! As if it mattered.
             把我的工作做完！老天！好像它真的很重要似的。

14. 要说真有什么的话;甚至正相反
      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.

      e.g. Living together didn't harm our friendship. If anything it strengthened it...
             在一起住并没有损害我们的友谊。要说真有什么的话,它反而巩固了我们的友谊。
      e.g. Asthma drugs are not addictive and you don't need to keep increasing the dose. If anything, the reverse is true.
             哮喘药物不会造成药物依赖,你不用持续增大剂量。甚至正相反,减小剂量才对。

15. 显然不是
      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.

      e.g. I am surprised by the fuss she's making. It's not as if my personality has changed.
             她的大惊小怪令我很吃惊。显然不是我的个性改变了。

16. (用于给人建议)如果我是你的话
      You say 'if I were you' to someone when you are giving them advice.

      e.g. If I were you, Mrs Gretchen, I just wouldn't worry about it...
             要是我是你,格蕾琴夫人,我一点都不会担心。
      e.g. What I'd do if I were you is be nice to him...
             如果我是你,我要做的就是对他好。