A human hair consists mainly of a protein called Keratin. It also contains some moisture and the trace metals and minerals found in the rest of the body. 

    人类的头发主要由一种叫角朊的蛋白质组成，并含有水分及在身体其他部分也可找到的微量金属和矿物质。 

    The only living part of hair is underneath the scalp--when the hair had grown through the scalp it is dead tissue. 

    头发唯一有生命的部分是在头皮下面，当它长出头皮时便成为无生命组织。 

    Hair’s natural shine is supplied by its own conditioner, sebum, an oil composed of waxes and fats and also containing a natural antiseptic that helps fight infection. Too much sebum results in greasy hair and conversely, too little sebum makes dry hair. 

    头发的自然光泽来自它自身的护发素：油脂，它含有蜡和脂肪，还含有抗感染的自然抗菌剂。油脂含量过多会导致油性发质，相反，油脂含量过少则会导致干性发质。 

    Hair grows about 12 mm per month. If a person never has his hair cut, it would grow to a length of about 107 cm before falling out. Hair grows faster in the summer and during sleep. A single strand lives for up to seven years. 

    头发每个月可长12毫米，如果一个人从不剪发，头发会长至107厘米才开始脱落。在夏天和睡觉的时候头发生长得较快。一根头发的寿命可长达7年。 
    
    Healthy hair is highly elastic and can stretch 20 or 30 per cent before snapping. A human hair is stronger than copper wire of the same thickness. A combined strength of a headful of human hair is capable of supporting a weight equivalent to that of 99 people. 

    健康的头发非常富有弹性，可拉长20％或30％而不断。一根头发比同等粗细的铜丝还要结实。满头头发合在一起的力量可经得起99个人的重量。 

    Scandinavians normally have thin, straight, baby-fine hair, and mid Europeans hair that is neither too fine nor too coarse. People native to the Indian subcontinent have coarse textured tresses while Middle Eastern populations have strong hair. The hair of Chinese and Japanese people is very straight; that of Latin-speaking and North African peoples can be very frizzy and thick. 

    斯堪的纳维亚人的头发又细又直，像婴儿的头发一样；中部欧洲人的头发不细不粗；印度次大陆人的头发粗且打绺；中东人的头发都很结实；中国人和日本人的头发非常直顺；而拉丁语国家及北非地区的人头发卷曲而浓密。