why don't+主語+動詞；why not一定要直接跟動詞，動詞前不能有其他成分。why don't結(jié)構(gòu)可以有時態(tài)的變化，比如變?yōu)檫^去why didn't，完成式why haven't等，why not沒有時態(tài)變化。why not可以獨立成句，而why don't不可以。

Why don't和Why not有何區(qū)別

這兩個句式,在表達"建議"時,是一樣的意思.既"(你)為什么不做.....?"或"(你)應該做.....".如:

Why don't you turn to the reference book?

Why not turn to the reference book?

"(你)為什么不看參考書呢?"也就是"你應該看一下參考書".

但是Why don't you do還可以作為一個疑問句使用,提出疑問.如:

Why didn't you see the football match?

"你為什么沒有看這場足球賽?"

why don't you ...? and why not...? are the same.

why not...? is short for why don't you...?they are used to give people suggestions.

why don't you ...? is a formal way.and why not is often used in oral English.

區(qū)別在三點：

1、兩個句子結(jié)構(gòu)不同

why don't + 主語 + 動詞；why not一定要直接跟動詞，動詞前不能有其他成分

2、why don't 結(jié)構(gòu)可以有時態(tài)的變化，比如變?yōu)檫^去why didn't，完成式 why haven't 等，why not沒有時態(tài)變化

3、why not可以獨立成句，而why don't不可以。

其實why not就是why don't you的省略形式.學英語的人應該都知道,在英語中,省略句要省就是主謂一起省.只不過前者在口語中更為廣泛的使用,且可以獨立成句.而后者則可以有時態(tài)的變化.

Why not和Why didn't區(qū)別

從時態(tài)上看，why not 一般現(xiàn)在時，表示現(xiàn)在還沒發(fā)生的事情，還有改變的機會。而why didn't是過去時態(tài)，已成定局了。

從含義上看，why not 和 why don't you 是近義句，都表達提議做某事。而Why didn't只是為什么當初沒有做某事。