do
v.aux.
Used with the infinitive without to in questions,negative statements,and inverted phrases:
用于疑問句、否定句和倒裝句跟不帶 to的不定式連用,見于問句、否句、倒裝句中：
Do you understand?I did not sleep well.Little did we know what was in store for us.
你懂嗎?我沒睡好.我們不清楚留給我們的是什么
Used as a means of emphasis:
用以強(qiáng)調(diào)：
I do want to be sure.Do be still!
我確實(shí)想肯定.安靜!
（在否定的陳述句和命令句里作為助動(dòng)詞）
He didn't come.
他沒來.
（在疑問句里作為助動(dòng)詞）
Did he arrive in time?
他按時(shí)到了嗎?
（作為助動(dòng)詞表示強(qiáng)調(diào)）
He did come after all!
他畢竟還是來了!
（作為助動(dòng)詞代替剛剛用過的或要在答覆時(shí)用到的動(dòng)詞）
He likes skating and so does she.
他喜歡滑冰她也喜歡滑冰.