Variation is a characteristic of language: there is more than one way of saying the same thing in a given language. Variation can exist in domains such as pronunciation (e.g., more than one way of pronouncing the same phoneme or the same word), lexicon (e.g., multiple words with the same meaning), grammar (e.g., different syntactic constructions expressing the same grammatical function), and other features. Different communities or individuals speaking the same language may differ from each other in their choices of which of the available linguistic features to use, and how often (inter-speaker variation), and the same speaker may make different choices on different occasions (intra-speaker variation).
While diversity of variation exists, there are also some general boundaries on variation. For instance, speakers across distinct dialects of a language tend to preserve the same word order or fit new sounds into the language's established inventory of phonemes (the study of such restrictions known as phonotactics, morphotactics, etc.); however, exceptions to these restrictions are possible too. Linguistic variation does not equate to ungrammatical usage of the language, but speakers are still (often unconsciously) sensitive to what is and is not possible in their native lect.