Comparative linguistics (originally comparative philology) is a branch of historical linguistics that is concerned with comparing languages to establish their historical relatedness.

In linguistics, the comparative is a syntactic construction that serves to express a comparison between two (or more) entities or groups of entities in quality, quantity, or degree; it is one of the degrees of comparison, alongside the positive and the superlative. The comparative is signaled in English by the suffix -er or by a word of comparison (as, more, less) and the conjunction- or preposition-like word as or than. The comparative is frequently associated with adjectives and adverbs because these words take the -er suffix or modifying word more or less (e.g., faster, more intelligent, less wasteful); it can also, however, appear when no adjective or adverb is present, for instance with nouns (e.g., more men than women). The syntax of comparative constructions is poorly understood due to the complexity of the data. In particular, the comparative frequently occurs with independent mechanisms of syntax such as coordination and forms of ellipsis (gapping, pseudogapping, null complement anaphora, stripping, verb phrase ellipsis). The interaction of the various mechanisms complicates the analysis. Most if not all languages have some means of forming the comparative, although these means can vary significantly from one language to the next.