yet一般式用在疑问句和否定句中,在肯定句中的一般句子是现在完成时态.而still一般是用在肯定句中,表示“依然、依旧”的意思.下面是他们的一些常见用法,希望这能帮到你区别他们.
yet 的用法：
在现在完成时的句子中,already常用于肯定句,yet常用于否定句和疑问句,但yet还有其他用法.
1.用于否定句中,意思是还、尚、迄今、到那时”.例如 he is not yet here.他还未到.at three o”clock they had not yet decided whether to play basketball or not.三点钟时他们尚未决定是否去打篮球.
2.用于疑问句中,意思是已经”.例如 is everything ready yet 一切都准备好了吗?
3.与比较级连用,意思是更”.例如 you must work yet harder.你还需更努力地工作.
4.与once ,again ,another 连用,意思是再”.例如 he has made yet another mistake.他又犯了一个错误.
5.用于肯定句中,意思是仍然、还得”.例如 she is yet a child.她还是个孩子.
6.用作并列连词时,意思是然而、可是”.例如 he studied hard yet he failed.他学习努力,可是考试仍未及格.
still的用法：
一、作形容词使用
1.still作为形容词时,指没有运动或动作的状态,相当于motionless,常译为“静止的”、“不动的”.例句：
(1) The doctor asked me to keep still.医生叫我不要动.
(2) The old woman sat still for about an hour.那个老妇人一动不动,坐了大约一个小时.
（3) Her hands were never still.她的双手从来不停歇.
2.still还可以指完全没有声响的,常译为“宁静的”、“平静的”、“寂静的”.例句：
(1) How still everything is!一切是多么寂静啊!
(2) The forest was very still.森林里非常寂静.
(3) The room was still at the end of the speech.演讲过后,室内一片寂静.
与calm不同的是,still常用于指生理上的安静,而calm则表示内在的平静状态,指人没有不安宁的表现或巨大的激动.例句：
(4) Even after his wife died he was calm.尽管他妻子死了,他仍很镇静.
(5) The night was very still.那天晚上很宁静.
二、作副词使用
1.still作副词使用时,含有“仍旧”、“还”之意,表示某事仍在继续,多用于肯定句或疑问句之中.例句：
(1) My mother is still cooking.我妈妈还在做饭.
(2) Her arm still hurts.她的胳膊还在痛.
(3) In spite of his shortcomings,the girl still loved him.尽管他有缺点,那个女孩仍然爱他.
(4) Are you still working there?你还在那里工作吗?
(5) Will you still go there tomorrow?明天你还会去那儿吗?
试比较：(6) He still stands.（副词） 他仍旧站着.
(7) Stand still.（形容词） 站好别动.
still有时也可用于否定句中,表示某事尚未完成或发生,此时,它要放于否定的助动词之前（在否定句中常用yet）.例句：
(8) She still hasn't come back.她还没有回来.
(9) I still don't understand.我仍旧不明白.
(10) The bus hasn't arrived yet.汽车还没有到达.
2.still还可以用来修饰比较级,相当于even,可译为“更”、“还要”、“甚”.例句：
(1) We must study still harder.我们必须更加努力地学习.
(2) It was cold yesterday,but today it is still colder.昨天天气很冷,可今天却更冷.
(3) Her sister is still taller.她妹妹个子还要高.
(4) They came still earlier.他们来得更早.
三、作连词使用
still作为连词时含有“尽管如此,可还是要”、“然而”、“不过”之意.例句：
(1) Although we are very tired,still we shall work.虽然我们很累,但我们还将工作.
(2) She was thirsty,still she wouldn't drink.她虽然渴了,但仍不喝东西.
(3) I like cats; still I don't care to own one.我虽然喜欢猫,但不愿意养猫.
(4) This is a very unpleasant affair.Still,we can't change it.这是件很不愉快的事,但是我们无法改变它.此外,still可以与more连用,相当于much more,常译“至于……更不必说”.例句：
She can speak English,still more Japanese.她连英语都会说,日语更不在话下.
still还可以和less连用,多用于否定句之后,相当于much less,常译为“更何况”、“更不用说”.例句：
I didn't even see her,still less speak to her.我见也没有见到她,更不用说和她说话了.