Diagram showing relationships between etymologically-related words
In historical linguistics, cognates or lexical cognates are sets of words in different languages that have been inherited in direct descent from an etymological ancestor in a common parent language.[1] Because language change can have radical effects on both the sound and the meaning of a word, cognates may not be obvious, and often it takes rigorous study of historical sources and the application of the comparative method to establish whether lexemes are cognate. Cognates are distinguished from loanwords, where a word has been borrowed from another language.
The term cognate derives from the Latin noun cognatus 'blood relative'.[2]
Cognates also do not need to look or sound similar: English father, Frenchpère, and Armenianհայր (hayr) all descend directly from Proto-Indo-European*ph₂tḗr. An extreme case is Armenian երկու (erku) and English two, which descend from Proto-Indo-European*dwóh₁; the sound change *dw > erk in Armenian is regular.
False cognates are pairs of words that appear to have a common origin, but which in fact do not. For example, Latin habēre and German haben both mean 'to have' and are phonetically similar. However, the words evolved from different Proto-Indo-European (PIE) roots: haben, like English have, comes from PIE *kh₂pyé- 'to grasp', and has the Latin cognate capere 'to seize, grasp, capture'. Habēre, on the other hand, is from PIE *gʰabʰ 'to give, to receive', and hence cognate with English give and German geben.[3]
Likewise, English much and Spanish mucho look similar and have a similar meaning, but are not cognates: much is from Proto-Germanic *mikilaz < PIE *meǵ- and mucho is from Latin multum < PIE *mel-. A true cognate of much is the archaic Spanish maño 'big'.[4]
Distinctions
Cognates are distinguished from other kinds of relationships.
Loanwords are words borrowed from one language into another, for example English beef is borrowed from Old French boef (meaning "ox"). Although they are part of a single etymological stemma, they are not cognates.
Doublets are pairs of words in the same language which are derived from a single etymon, which may have similar but distinct meanings and uses. Often one is a loanword and the other is the native form, or they have developed in different dialects and then found themselves together in a modern standard language. For example, Old French boef is cognate with English cow, so English cow and beef are doublets.
Translations, or semantic equivalents, are words in two different languages that have similar meanings. They may be cognate, but usually they are not. For example, the German equivalent of the English word cow is Kuh, which is also cognate, but the French equivalent is vache, which is unrelated.
Related terms
The etymon, or ancestor word, is the ultimate source word whence one or more cognates derive. For example, the etymon of both Welsh ceffyl and Irish capall would be the Proto-Celtic *kaballos (all meaning horse). Outside of historical linguistics, a parallel term for an etymon is a root or root word. In this usage however, the analysis is limited to within a single language rather than across separate languages. Run, as such, can be said to be the root of both running and runs, while happy would be the root word of such others as unhappiness or happily.
A derivative is any word coming from a particular etymon. Similar to the distinction between etymon and root above, a nuanced distinction can sometimes be made between a derivative and a descendant. Descendant can be used more narrowly within the context of historical linguistics to emphasize a word inherited across a language barrier. For example, Russian мо́ре and Polish morze are both descendants of Proto-Slavic *moře. By contrast, within the study of morphological derivation, unhappy, happily, and unhappily are all derivatives of the word happy.
^"cognate", The American Heritage Dictionary of the English Language, 4th ed.: "Latin cognātus: co-, co- + gnātus, born, past participle of nāscī, to be born." Other definitions of the English word include "[r]elated by blood; having a common ancestor" and "[r]elated or analogous in nature, character, or function".
