as的用法
1、as做介詞，意思是“作為”
例句：
French is known as the most beautiful language in the world.
法語以世界上最美麗的語言著稱。
2、as做連詞，引導時間狀語從句，意思是“當……的時候”
例句：
My mother was cooking fish as I arrived home.
當我到家的時候，我媽媽正在做魚。
3、as做連詞，引導原因狀語從句，意思是“因為”
例句：
As rain has fallen, the air is cooler.
因為下過雨，所以空氣比較涼爽。
4、as做連詞，引導讓步狀語從句，意思是“雖然”
例句：
Young as he is, he has been one of the most famous painters in our country.
雖然他還很年輕，但已經(jīng)成為我們國家最有名的畫家之一。
5、as做連詞，引導方式狀語從句，意思是“以……方式”
例句：
Do as the Romans do when in Rome.
入鄉(xiāng)隨俗
6、as做關系代詞，引導定語從句
例句：
This is the same game as I played yesterday.
這和我昨天玩的游戲一樣。
though用作連詞，有雖然，即使等含義。用作副詞時，有不過，可是，然而等含義。though引導的讓步狀語從句可用部分倒裝的形式。
though的用法
一、用作連詞
表示“雖然”，although 比 though 更為正式：兩者大致同義，可換用。
Though （Although）it was barely four o’clock, the lights were already on.
盡管才四點鐘，燈已經(jīng)亮了。
Though （Although）we are poor, we are still happy.
我們雖然窮，仍然很快活。
二、用作副詞
though 可用作副詞，一般放在句末(不放在句首)，意為“可是”、“不過”。
I like him. Though he makes me angry sometimes.
我喜歡他，不過他有時惹我生氣。
三、用于倒裝
though 引導的讓步狀語從句可用部分倒裝的形式(注意：倒裝后位于句首的名詞之前不用冠詞)