1.already多用于肯定句,而yet多用于疑问句或否定句作“已经”“还”“仍然”解,通常放在句末。
The guests have already arrived.客人已经到了。
Have the guests arrived yet?客人到了吗?
The guests have not arrived yet.客人还没到。
2.already有时也可用于疑问句中表示惊讶、怀疑,或者表示期望〔预计〕有一个肯定的回答。试比较以下两个句子:
Have you had your lunch yet?
你吃过午饭了吗?(一般疑问句)
Have you had your lunch already?
你已经吃过午饭了?(表示惊讶)
Have you received your invitation yet?
你收到邀请信了吗?(一般疑问句)
Have you already received your invitation?
你已经收到邀请信了吧?(料想已收到,想证实)
3.yet有时也可用于肯定句中,可表示“还”“尚”,有时含有“还为时太早”之意; 与形容词或副词的比较级连用时意为“甚至,更”“还要”,与最高级连用意为“到目前〔当时〕为止(最…)”。