thigh:
n. 大腿,股
His thigh was badly injured in a car accident.
他的大腿因为车祸受了很严重的伤。
The fitness instructor wants me to work out my thighs.
健身教练要我多锻炼一下大腿。
leg:
n. 腿;支柱
He legged it as soon as he saw the teacher.
他一看到老师就立即逃走了。
One leg of the table is shorter than the others.
其中一只桌子腿比其他的桌子腿短一截。