Siffa kalma ce da ke bayyana ko gyara suna ko karin magana ta hanyar samar da ƙarin bayani game da ingancinta, yanayinta, ko halayenta. Siffofin suna iya isar da sifofi daban-daban kamar girman, siffar, launi, shekaru, asali, asalin ƙasa, da sauransu. Misali, a cikin jumlar “motar shuɗi” “blue” sifa ce da ke bayyana launin motar. Ana iya amfani da sifa don yin kwatance, kamar "tsawo," "ƙananan," "mafi sauri," ko don nuna ƙimar inganci, kamar "sosai," "matuƙar," ko "dan kadan." Siffai muhimmin sashe ne na harshe kuma ana amfani da su a cikin magana da rubutu don samar da cikakkun bayanai dalla-dalla.