Reduplication is the process of repeating a word or part of it to express some grammatical function, plurality for example. It is used in some language families' grammar, most notably in Malayo-Polynesian where it forms plurals:
Bahasa Malay rumah, house, rumah-rumah, houses.
Hawaiian has the important example of Wiki-wiki!
Go, “look”, Go-go, “examine with attention”.
Chinese also uses reduplication:
ren, “person”, renren, “everybody”
- spondeo, spopondi (Latin, “I vow, I vowed”)
- λείπω, λέλοιπα (Greek, “I am missing, I was missing”)
- háitan, haíháit (Gothic, “to name, I named”)
See also: augment