一、用作介詞，表示在...上；向，朝等含義。
The book is on the table.
書在桌子上。
The spider is walking on the ceiling.
蜘蛛在天花板上爬行。
They made their own judgment on his report.
他們憑他的報告作出自己的判斷。
二、用作副詞，表示向前（移動），進(jìn)行著等含義。
Put your coat on.
穿上你的`大衣.
Move on!
向前走！
She worked quietly all night.
她整個晚上默默地繼續(xù)工作。
三、用作形容詞，表示在進(jìn)行的，在發(fā)生的等含義。
The televisionw set was on.
電視機開著。
The light were all full on.
燈火通明。