The suffix -ism denotes a distinctive system of beliefs, myth, doctrine or theory that guides a social movement, institution, class or group. For example, baptize (literally derived from "to dip") becomes "baptism," a distinctive system of cleansing in water to testify to the forgiveness of sins. It's taken from the Greek suffix -ismos, Latin -ismus, and Old French -isme, that forms nouns from verbal stems. Greek baptismos "immersion", for example,'s derived from baptizein, a Greek verb meaning… (More on -ism)