The subfields of grammar are phonetics, phonology, morphology, syntax, and semantics.
Linguists recognise a number of types of grammar.
Grammars evolve through usage and human population separations. With the advent of written representations, formal rules about language usage tend to appear also. Formal grammars are codifications of usage that are developed by observation. As the rules become established and developed, the prescriptive concept of grammatical correctness can arise. This often creates a gulf between contemporary usage and that which is accepted as correct. Linguists normally consider that prescriptive grammars do not have any justification beyond their authors' aesthetic tastes. However, prescriptions are considered in sociolinguistics as part of the explanation for why some people say "I didn't do nothing", some say "I didn't do anything", and some say one or the other depending on social context.
The formal study of grammar is an important part of education from a young age through advanced learning, though the rules taught in schools are not a "grammar" in the sense most linguists use the term, as they are often prescriptive rather than descriptive.
Planned languages are more common in the modern day. Many have been designed to aid human communication (such as Esperanto) or created as part of a work of Fiction (such as the Klingon language and Elvish language). Each of these artificial languages has its own grammar.
Programming languages used for the purpose of computer programming (such as Java) have grammars, but do not resemble human languages very much. These are called formal grammars. In particular, they conform precisely to a grammar generated by a pushdown automaton with arbitrarily complex commands. They usually lack questions, exclamations, simile, metaphor and other features of human languages.
It is a myth that analytic languages have simpler grammar than synthetic languages. That languages have different levels of grammatical complexness can be shown to be false by realizing the fact that changes to words are not the only kind of grammar. Chinese is very context dependent. In other words, context accomplishes the same role as declension and conjugation. (Chinese does have some inflections, and had more in the past.) Latin, which is synthetic, uses affixes and inflections to accomplish the same role that Chinese does with syntax. Because Latin words are quite (though not completely) self-contained, a sentence can be made from scattered elements. In short, Latin has a complex affixion and a simple syntax, while Chinese has the opposite.
In computer science, the syntax of each programming language is defined by a formal grammar. In theoretical computer science and mathematics, formal grammars define formal languages. The Chomsky hierarchy defines several important classes of formal grammars.Grammars of specific languages
Grammatical terms
Grammatical devices
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