From Hull AWE
The basic meaning of cognate is 'sharing an ancestor', or 'related'. In the terminology of language studies, it is used specifically for:
- words. Cognate words are those which can be traced back to the same root, as for example the English 'brother' and the German 'bruder' are cognate. It may seem less obvious that the Latin pater is cognate with the English 'father' and German 'vater', but the shift from '-p-' in Romance languages to '-f-' in Germanic languages is so regular that it forms the first of Grimm's Laws, the beginnings of modern scientific etymology.
- languages. Cognate languages are those which descend from the same parent, so that the Romance languages French, Italian and Spanish are all new forms of Latin, the language of the Empire that two thousand years ago ruled the territories in which they are now spoken.