Gashi filament na furotin ne wanda ke tsiro daga follicles da aka samu a cikin dermis. Gashi yana daya daga cikin ma'anar dabi'ar dabbobi masu shayarwa. Jikin ɗan adam, baya ga wuraren fata masu kyalli, an lulluɓe shi da ɓangarorin da ke samar da kauri mai kauri da gashi mai laushi. Mafi yawan sha'awar gashi an mayar da hankali ne akan girman gashi, nau'in gashi, da kuma kula da gashi, amma gashi kuma muhimmin abu ne na halitta wanda ya ƙunshi furotin, musamman alpha-keratin.
Halayen ga nau'ikan gashi daban-daban, kamar gyaran gashi da cire gashi, sun bambanta a cikin al'adu daban-daban da lokutan tarihi, amma galibi ana amfani da su don nuna aƙidar mutum ko matsayinsa na zamantakewa, kamar shekarunsa, jinsi, ko addininsa.