2
over/above/ on 都可以表示“在......上之意。具体区别：
1）over：长表示恰好垂直的位置关系，或者含有空间上接近的含义。其
反义词为under.如：
There is a bridge over the river.
My pen is now under your desk.
2）above:只笼统的表明“高于......;在......之上”，多指在相对较高位置。其反义词是below。如：
We flew above the clounds.
表示“高于某个抽象水平”或“温度zero degree以上多少度”用above。
His work is well above the average.
The temperature is three degrees above zero.
The temperature is above/over 30 "C.温度高于...时可互用。
3）on:"...表面上”，强调与表面接触。其反义词为beneath[正式语体，现代英语中多用比喻义。如：
There are some books on the desk.
The village was situated beneath a wooden hill.村庄位于林山下。