Dyadic kinship terms (abbreviatedDY orDYAD) arekinship terms in a few languages that express the relationship between individuals as they relate one to the other. In English, there are a few set phrases for such situations, such as "they are father and son", but there is not a singledyadic term that can be used the way "they are cousins" can; even the latter is not truly dyadic, as it does not necessarily mean that they are cousinsto each other. The few, and uncommon, English dyadic terms involvein-laws:co-mothers-in-law,co-fathers-in-law,co-brothers-in-law,co-sisters-in-law,co-grandmothers, andco-grandfathers.
Examples of dyadic terms for blood kin includeKayardild (Australian)ngamathu-ngarrba "mother and child", derived fromngamathu "mother", andkularrin-ngarrba "brother and sister", fromkularrin "cross-sibling", with the dyadic suffix-ngarrba. Not all such terms are derived; theOk languageMian has a single unanalysable rootlum for "father and child".[1]
Dyadic blood-kin terms are rare inIndo-European languages. Examples areIcelandic andFaroese, which have the termsfeðgar "father and son",feðgin "father and daughter",mæðgin "mother and son",mæðgur "mother and daughter".[1]
Chinese and Japanese usecompound nouns to make dyadic terms, such as (in Japanese)親子oyako "parent and child",兄弟kyōdai "brothers; siblings",姉妹shimai "sisters", and夫婦fūfu "husband and wife".
The languages which have such terms are concentrated in the western Pacific. There are at least ten in New Guinea, includingOksapmin,[2]Menya, and the Ok languages; fifteen or moreAustronesian languages, from Taiwan to New Caledonia; and at least sixty in Australia, such as Kayardild above. There are sporadic examples in Northern Eurasia, including a fewTurkic andUralic languages,Yukaghir, andAinu; depending on definitions, theYi languages of Southeast Asia may also be said to have such terms. Elsewhere they are rare, or at least have not been described. Known languages include Athabaskan (Koyukon andCarrier),Pomo, andSouthern Paiute in North America,Quechua, Paezan (Nasa Yuwe), and Cariban (Tiriyo) in South America,Adyghe in the Caucasus, andKhoe (Kxoe,Gǀwi) in southern Africa.[1]