直接加s构成复数,因它是可数名词.
下面是来自牛津的权威解释：
/ heE(r); hZr/ n
(a) [C] one of the fine thread-like strands that grow from the skin of people and animals （人或动物的）毛发（指单根）:two blonde hairs on his coat collar 留在他外衣领子上的金发女子的两根头发 * There's a hair in my soup.我的汤里有根毛.(b) [U] mass of these,esp on the human head 毛发; （尤指）头发:have one's `hair cut 理发 * have long,black hair 长着一头长﹑ 黑发 * a cat with a fine coat of hair 长着一身好毛的猫.(c) [C] thread-like growth on the stems and leaves of some plants （某些植物的茎和叶上长的）茸毛.
有问题还可以再问.
