Lanugo 毫毛

Lanugo (/ləˈnuːɡoʊ, -ˈnjuː-/; from Latin lana "wool") is very fine, soft, usually unpigmented, downy hair that is sometimes found on the body of a fetus or newborn baby. It is the first hair to be produced by the fetal hair follicles, and it usually appears at about five months of gestation. It is normally shed before birth, around seven or eight months of gestation, but is sometimes present at birth. It disappears on its own within a few days or weeks.

毫毛 

毫毛是非常纤细、柔软的，通常是无色素的，绒毛似得毛发，它有时候发现在胎儿或新生儿的体表。它是有胎儿毛囊产生的最早的毛发，且通常在孕5个月时出现。正常情况下，出生前，约7～8个月时脱落，但是有时在出生后也会见到，且在数天或数周内消失（俗称胎毛）

Vellus hair 汗毛 (在很多字典上，也把它翻译成毫毛，与lanugo混淆）

Vellus hair is short, fine, light-colored, and barely noticeable thin hair that develops on most of a person's body during childhood. Exceptions include the lips, the back of the ear, the palm of the hand, the sole of the foot, some external genital areas, the navel and scartissue. The density of hair  the number of hair follicles per area of skin – varies from person to person. Each strand of vellus hair is usually between 2 mm and 2cm  long and the follicle is not connected to a sebaceous gland.

汗毛

汗毛是一种短小，纤细、浅色的体毛，几乎不容易注意到。在儿童期多数人出会出现汗毛。唇、耳背、掌跖、某些外生殖器区域、肚脐眼和瘢痕组织没有汗毛。汗毛的密度因人而异，（西方人通常比我们中国人密度高，译者注）。汗毛通常2mm～2cm之间，汗毛毛囊不与皮脂腺连接。

Terminal hair 刚毛

Terminal hair are the "normal" long, thick hair that grow on the scalp, face,chest and arms before puberty; after puberty they also grow at secondary hair sites i.e. on the axillae, arms and legs. These grow from follicles that have sebaceous glands. In conditions such as male and female pattern baldness, hairs in these so-called 'terminal follicles' can gradually become thinner and shorter to mimic vellus hairs.

刚毛

刚毛是一种“正常”长的、粗的毛发，青春期前生长在头皮、脸部、胸部和手臂。青春期后刚毛也可以长在第二毛发位点，如腋下、手臂和下肢。这些毛囊伴有皮脂腺生长。在男性型和女性型脱发中，这种所谓刚毛毛囊会逐渐变成纤细而短小的类似于汗毛的毛发。

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浙江省人民医院皮肤科 潘卫利译，2017-11-12