Ƙarƙashin ƙasa, wanda kuma aka sani da kyakkyawa quark, wani nau'in barbashi ne na farko wanda ke cikin dangin quarks. Yana ɗaya daga cikin nau'ikan quarks guda shida, tare da sama, ƙasa, fara'a, ban mamaki, da manyan ƙuƙumi. A kasan Quark shi ne na uku-na uku-na uku quah quict, kuma yana da mummunan cajin wutar lantarki na -1/3 muhimmiyar rawa wajen lalata wasu barbashi, kamar B mesons, da kuma samar da Higgs bosons. An fara gano shi a cikin 1977 ta hanyar ƙungiyar masana kimiyya a Fermilab a Illinois, Amurka.