In reduplication new words are made by doubling a stem, either without any phonetic changes as in bye-bye (coll, for good-bye) or with a variation of the root-vowel or consonant as in ping-pong, chit-chat (this second type is called gradational reduplication).
Stylistically speaking, most words made by reduplication represent informal groups: colloquialisms and slang. E. g. walkie-talkie ("a portable radio"), riff-raff ("the worthless or disreputable element of society"; "the dregs of society"), chi-chi (sl. for chic as in a chi-chi girl).
