In linguistics, the grammar of a natural language is its set of structural constraints on speakers 'or writers' composition of clauses, phrases, and words. The term can also refer to the study of such constraints, a field that includes domains such as phonology, morphology, and syntax, often complemented by phonetics, semantics, and pragmatics. There are currently two different approaches to the study of grammar, traditional grammar and theoretical grammar.
A vowel is a syllabic speech sound pronounced without any stricture in the vocal tract. Vowels are one of the two principal classes of speech sounds, the other being the consonant. Vowels vary in quality, in loudness, and also in quantity (length). They are usually voiced and are closely involved in prosodic variations such as tone, intonation, and stress. The word vowel comes from the Latin word vocalis, meaning "vocal" (i.e., relating to the voice). Thus, in English, the word vowel is commonly used to refer to vowel sounds and the written symbols representing them (a, e, i, o, u, and sometimes y).