头发 [词典] hair; pile; hair on a human head; [电影] La chevelure; [例句]他的头发已灰白了。His hair has turned grey.毛发 [词典] hair (on the human body and head); [例句]他为一本女性杂志秀出了他那肌肉发达、毛发浓密的性感胸部。He bared his muscular, hairy chest for a women's magazine.
hair可以表示一个人所有的头发（头发整体）,这时候是不可数名词,不可以在后面直接加S,例如：Her hair covers her face. 又或者He has got short black hair.但是当hair表示一根,两根的发丝、毛发时,是可数的。 可以说a hair,a few hairs
