Reduplication is a morphological process that involves the repetition of all or part of a word. These parts of words are referred to as roots or stems. Some languages utilize the process extensively, some moderately, and some not at all.
Morphological processes change the stem of a word in order to adjust its meaning for communicative purposes. Roots are the parts of words that cannot be further broken down, meaning they are the most morphologically simple part of any word. Some words only contain a root, while others contain a root and a number of stems. A stem may be made up of only a root, but may also contain derivational and inflectional affixes.
The function and meaning of reduplication varies widely across languages. Many well-known examples are from languages in which the process is used to express the plural form. In these languages, depending on whether they show full or partial reduplication, either all or part of a noun is repeated.
In full reduplication, the entire word is repeated. Only a segment is duplicated in partial reduplication. The segment that is duplicated may occur at either the beginning or end of the word.
An example of a partially reduplicated word can be seen in Marshallese. The word kagir means 'belt.' To say 'to wear a belt' in Marshallese, one says kagirgir. This pattern is repeated when speaking of articles of clothing.
The concept is particularly interesting to linguists because it is an area that demonstrates an interface between phonology and morphology, meaning that these two parts of language intersect to create the process. Although the process is classified as morphological, phonology is also involved because the phonological segments are what is reduplicated. Phonological parts of the word are used for a morphological process.
Reduplication is a formal grammatical process in many languages. In English, it is infrequent and mostly informal. Slang words such as super-duper and razzle-dazzle express extra meaning using partial reduplication. This is identified as partial because the -s from super becomes a -d, and the -r from razzle also becomes a -d, meaning that the whole segment is not copied.
Many Austronesian languages, spoken in an area that stretches between Taiwan in the North, Madagascar in the West, and Hawaii in the East, have full and partial reduplication. Indonesian, the Austronesian language with the most speakers, makes extensive use of the process, most notably with plural number marking. An example of this is the word for house, rumah. To refer to houses, rumah-rumah is the correct form.