 In the strict sense, a proto-language is the most recent common ancestor of a language family, immediately before the family started to diverge into the attested "daughter languages".It is therefore equivalent with the "ancestral language" or "parental language" of a language family.Moreover, a group of languages (such as a dialect cluster) which are not considered separate languages (for whichever reasons) may also be described as descending from a unitary proto-language.