Cognate

In historical linguistics, cognates or lexical cognates are sets of words that have been inherited in direct descent from an etymological ancestor in a common parent language.

Because language change can have radical effects on both the sound and the meaning of a word, cognates may not be obvious, and it often takes rigorous study of historical sources and the application of the comparative method to establish whether lexemes are cognate. It can also happen that words which appear similar, or identical, in different languages, are not cognate.

Cognates are distinguished from loanwords, where a word has been borrowed from another language.

The English term cognate derives from Latin cognatus, meaning "blood relative".

For an example, cognates with the English word night can be found in most major Indo-European languages, including German Nacht, Swedish natt, Polish noc, Russian ночь noch, Lithuanian naktis, Welsh nos, Greek νύχτα nychta, Sanskrit नक्त nakt-, Albanian natë, Latin nox (gen. sg. noctis), Italian nottecode: ita promoted to code: it , French nuit, and Portuguese noite. These all mean 'night', and derive from the Proto-Indo-European *nókʷts with the same meaning. The Indo-European languages have hundreds of such cognate sets, though few of them are as neat as this.

The Arabic سلام salām, the Hebrew שלום shalom, the Assyrian Neo-Aramaic ܫܠܡܐ shlama and Amharic ሰላም selam 'peace' are cognates, derived from the Proto-Semitic *šalām- 'peace'.

The Paraguayan Guarani panambi, the Eastern Bolivian Guarani panapana, the Cocama and Omagua panama, and the Sirionó ana ana are cognates, derived from the Old Tupi panapana 'butterfly', maintaining their original meaning in these Tupi languages. Brazilian Portuguese panapanã (flock of butterflies in flight) is a borrowing rather than a cognate of the other words.

Cognates need not have the same meaning, as they may have undergone semantic change as the languages developed independently. For example English starve and Dutch sterven 'to die' or German sterben 'to die' all descend from the same Proto-Germanic verb, *sterbaną 'to die'.