A proto-language is a hypothetical, reconstructed language that is believed to be the common ancestor of a group of related languages. Linguists use comparative methods to identify similarities and differences among languages, allowing them to infer the features of this ancestral language. For example, the Proto-Indo-European language is the reconstructed ancestor of many modern languages, including English, Spanish, and Hindi. Proto-languages are not directly attested in written form; instead, they are inferred from the study of descendant languages. By analyzing vocabulary, grammar, and sound changes, researchers can piece together aspects of these ancient languages. Understanding proto-languages helps linguists trace the evolution of languages and the relationships between different language families.