Ma'anar ƙamus na kalmar "tushen kalmar" ita ce: Kalma ce ta asali, wadda ke aiki a matsayin ginshiƙin samuwar wasu kalmomi ta ƙara prefixes da suffixes. A cikin ilimin harshe, tushen kalmar kuma ana kiranta da kalmar tushe ko kalma mai sauƙi. Siffar siffa ce (mafi ƙarancin ma'ana na harshe) wanda ke ɗauke da ma'anar ƙamus na farko na kalma kuma ba za a iya ƙara rarraba shi zuwa ƙananan raka'a tare da ma'ana daban ba. Tushen kalmomin suna yawanci suna, fi'ili, ko sifa kuma suna ba da tushen ƙirƙirar wasu kalmomi da yawa a cikin harshe.