其实hair这个词既可以是可数名词,也可以是不可数名词,只是含义稍有变化：
1.作为可数名词,是指一根一根的头发或毛发：
Look at this,a hair in my soup.你瞧,我的汤里有根头发.
The cat has left her loose hairs all over my clothes.猫掉的毛弄得我衣服上到处都是.
My father has quite a few gray hairs.我父亲已有不少白发.
There is not a gray hair on his head.他头上没有一根白头发.
2.作为不可数名词头发的总称,是集合名词：
I’ll have my hair cut.我要去理发.
He has blond hair.他有一头金发.
She has a beautiful head of hair.她有一头漂亮的头发.
The woman likes to do her hair in foreign style.这个女人喜欢把头发梳成外国式.
试比较以下句子：
He has grey hair.他满头白发.