In linguistics, the modification of root words (lexemes) with grammatical markers (i.e., inflectional morphemes such as suffixes and prefixes) to fit different syntactic contexts, which includes conjugation of verbs and declension of nouns. (Compare derivational morphology.)
Most European languages tend to be highly inflected. Such languages are termed synthetic languages since they build new words by adding morphemes. English has lost most of its inflection and is considered an analytic language.