(1) up to now/then意思是“到目前，迄今；到那时(指过去或将来)”，较随便。up till now/then与之意思相同，但较为正式(关于up to now,另见“so far...”条)。
- Up to/till now the weather has been very hot.
天气直到现在还非常热。 - Up to then the work was good, but we encountered some unexpected problems later.
直到那时这项工作一切良好，但后来我们遇到了一些出人意料的问题。 - I'm going to Washington in mid-September, but up to/till then I'll be here.
我打算9月中旬去华盛顿，但直到那时我都会待在这儿。
(2) up to this/that moment指“到目前(那时)”，与up to now/then同义，为正式用语。
(3) so far意为“迄今，到目前”，等于up to the present/moment，谓语多用现在完成式(关于so far,另见“so far...”条)。
- So far the weather has been good, but I think it is going to rain later today.
到目前天气还一直很好，但我认为今天晚些时候会下雨。
(4) yet多用于否定句，疑问句，常用在句尾，也可紧接在not之后，主要有以下几个意思：
①此刻，现在。
- It's not time to go yet .
现在还不到走的时间。
②那时，当时。
- It was not yet time to go.
那时还不到走的时候。
③到现在，到目前，迄今(谓语多用现在时或现在完成时)。
- I haven't read much of it yet .
到目前，我还没读多少。 - The job is not yet finished.
这项工作目前还没完成。
④现在和以往一样；仍旧；还。
- He is yet a child. Don't be too hard on him.
他还是个孩子，不要对他太严厉。
⑤在将来。
- Our plan may yet succeed.
我们的计划可能会成功。
(5) as yet意为“到目前还……，到那时还……”。
- The plan has worked well as yet .
到目前为止计划进展顺利。 - As yet , Shakespeare had not become famous.
那时，莎士比亚还未出名。
(6) not just yet意为“暂时还不能(行)”。
- I can't come just yet .
我暂时还不能来。 - A: Are you going home?
你要回家吗？
B: No, not just yet .
不，暂时还不。
(7) by now/then意为“到现在，到这时/那时(可指过去也可指将来)”，与by this/that time意思相同。句子谓语多用完成时，但与be等表状态的词连用时，也可用一般时态。
- I hope you've understood by now what I mean.
我希望现在你能明白我的意思了。 - He left Edinburgh nine hours ago by car, he should be in London by now .
他9小时前乘车离开了爱丁堡，现在应在伦敦了。 - By then he was in his late thirties.
到那时他已三十好几了。 - I'll be back by then .
到那时我会回来的。
(8) ①already指“(到某一时间之前)已经”。
- He had already gone when I arrived.
我到那儿的时候他已经走了。
②already还可表示“(以前) 已经”。
- I've been there already and don't want to go again.
我已去过那儿，不想再去了。
③already也可表示“(比预计的快或早)已经”。
- You have had your breakfast already ? What a good boy you are!
你已经吃过早饭了？真是个好孩子！
