Theory of grammar as a branch of linguistics
Linguistics is the scientific study of human languages which is characterized by the systemic approach to the object of its investigation.
Grammar is one of the main linguistic disciplines which studies the grammatical system of language. The grammatical system is the whole set of regularities determining the combinations of words in the formation of utterances.
The nature of grammar is better understood in the light of discriminating the two planes of language — the plane of content and the plane of expression. The plane of content comprises the purely semantic elements contained in language; the plane of expression
The two planes are inseparably connected. Grammatical elements of language present a unity of content and expression, or a unity of form and meaning.
Language is a system of signs (meaningful units) which are closely interconnected and interdependent.
Speech is the manifestation of the system of the lan-ge in process of intercourse. Language and speech are inseparable, they form together an organic unity.
E.g. For some reason Dill started crying and couldn’t stop (content).
She started to cry again (plane of expression).
So, the aim of theoretical grammar of a language is to present a theoretical description of its grammatical system, i.e. to scientifically analyze and define its grammatical categories and study the mechanisms of grammatical formation of utterances out of words in the process of speech making.