三、副词 yet 用于现在完成时作“已经”讲，只用于否定句和疑问句中
1. Have you seen such a space shuttle yet?
你(已)见过这样的航天飞机吗?
2. Has the bell rung yet?
铃已打过了吗?
3. The bell has not been repaired yet.
铃尚未修好。
注：在肯定句中表示“已经”要用 already，不能用 yet。若在疑问句中用 already 代替 yet，则表示惊异的语气。
eg: Has the bell rung already? 铃真的打过了吗?
四、连词 yet 和 and yet, but yet 用法举例
1. It is very good, yet ( 或 but) it can be better.
这很好，但还能精益求精。
2. It is strange, and yet it is true. ( =It is strange yet ( 或 but) true.)
真奇怪，却是真的。
3. Air has weight, and yet it is very light.
空气有重量，虽然很轻。
4. Although this matter sounds strange, yet it is true.
此事听起来虽然奇怪，但却是事实。
5. The wheel is the simplest yet (或but) perhaps the most remarkable of all inventions.
轮子是所有发明中最简单却也许是最非凡的一种。
6. Everyone thinks that this is a simple method, (but) yet he cannot believe it.
大家都认为只是个简单方法，但他不信。
五、词组 as yet (到目前为止)和 just yet (就在此刻)常用于否定句中
1. They have not made such an advanced computer as yet.
他们目前尚未制造出这样一种先进的计算机。
2. No one has as yet been able to produce the absolute zero of temperature.
还没有人能产生绝对零度。
3. It will not happen just yet.
此事一时尚不至于发生。
