cognacy

The relationship between cognates; the condition of sharing a common ancestor term in another language.

First, in depending on vocabulary, as opposed to morphology or grammar, one runs the risk of assuming cognacy between similar words when the real explanation is borrowing.

The degree to which two languages share cognates, usually expressed as a percentage

In Table 13.1 are given the percentages for the degrees of cognacy between pairs of languages in the Upper Cross group.