Ma'anar ƙamus na kalmar "leukocyte" wani nau'in farin jini ne wanda ke taka muhimmiyar rawa a cikin tsarin garkuwar jiki ta hanyar kariya daga cututtuka da abubuwa na waje. Leukocytes kuma an san su da fararen sel ko fararen jini kuma an kafa su a cikin bargo. Akwai nau'o'in leukocytes daban-daban, ciki har da lymphocytes, monocytes, neutrophils, eosinophils, da basophils, kowannensu yana da takamaiman ayyuka a cikin tsarin rigakafi.