Word for the Wise July 31, 2006 Broadcast Topic: Duplication and reduplication
On this seventh day of the seventh lunar month, we take note of the Chinese Double Seven Festival. (来源：英语杂志 http://www.EnglishCN.com)
Today's celebration corresponds roughly to the western Valentine's Day; it has its origin in the mythological lovers Cowherd and the Weaver Maid, who are permitted to meet only once each year, on this day.
As bittersweet as their story is, we're more intrigued by the Chinese appreciation of doubles. In addition to the seventh day of the seventh lunar month, traditional Chinese celebrations fall on the first day of the first month, the fifth day of the fifth month, and the ninth day of the ninth month.
And that leads us to the terms duplication and reduplication and to their application in English. Duplication is another word for a counterpart, or one that resembles or corresponds exactly to another. Reduplication names "an act or instance of doubling or reiterating." It also names "an often grammatically functional repetition of a radical element or a part of it occurring usually at the beginning of a word and often accompanied by change of the radical vowel."
Girly-girly and goody-goody are called reduplications, and so are hoity-toity and jingle-jangle. So why isn't girly-girly called a duplication and jingle-jangle a reduplication? They could be differentiated that way, but because words created by reduplication (that is, by repetition of a radical element accompanied by change in the radical vowel) are more common, it seems perfectly fine for reduplication to serve (fittingly enough) a dual purpose.