Proto-Celtic is the presumed ancestor language of all the known Celtic languages.

Two languages are genetically related if they descended from the same ancestor language.

The case system of the ancestor language, Latin, has been lost except in pronouns.

Kawi is the ancestor language of modern Javanese.

The relatively few linguists who have discussed the subject disagree on how much can be known of the ancestor language.

Less conservative linguists have advanced proposals on the vocabulary and syntax of the ancestor language.

By studying words that exist in all languages, linguists can reconstruct the ancestor language.

A given programming language does not usually have a single ancestor language.

Proto-Mongolic is the hypothetical ancestor language of the modern Mongolic languages.

Languages are categorized under the ancestor language with the strongest influence.