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In linguistics, the comparative method is a technique for studying the development of languages by performing a feature-by-feature comparison of two or more languages with common descent from a shared ancestor, as opposed to the method of internal reconstruction, which analyzes the internal development of a single language over time.

Ordinarily both methods are used together to reconstruct prehistoric phases of languages, to fill in gaps in the historical record of a language, to discover the development of phonological, morphological, and other linguistic systems, and to confirm or refute hypothesized relationships between languages.