头发是可数名词还是不可数
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。
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。
Mary\'s red hair always made her conspicuous at school.
玛丽的红头发在学校里总是很惹眼。
Did you see the length of his hair?
你看见他头发有多长吗？
Your hair could do with a cut.
你该理发了。