P honological, grammatical and lexical systems are parts of language. They are closely connected. This can be proved by the fact that as linguistic disciplines they study the same object but from different points of view.

Phonetics presents the material side of language. Lexicon deals with naming the most relevant things of the material and non-material world. Grammar helps organize thought according to the rules of a concrete language.

The description of the phonological system is given by phonetics. Concrete lexical meanings of separate words are studied by lexicology. But the same words belong to different parts of speech, and thus are characterized by special grammar categories and forms.

Sometimes grammatical forms determine certain changes in the lexical meaning of words. e. g. to go is a verb of motion but in its continuous form and followed by an infinitive it means 'intention to fulfill an action in the immediate future'. Thus, the lexical meaning is grammatically conditioned here. A case when a grammar form gives rise to a new lexical unit is called lexicalization. e. g. The plural form of the word colour – colours has got the meaning of 'a banner'. Historically grammar inflexions are derived from pronouns and prepositions. When words become grammar endings it is a case of grammaticalization.

The ties between lexicology and grammar are especially strong in the sphere of word-derivation. This part of linguistics lies on the borderline between lexicology and grammar and it is studied by both of them.

Grammar is a set of principles by which a language functions.

Grammar as a linguistic discipline falls into practical (normative, or descriptive) and theoretical. Practical Grammar gives the description of the grammatical system of a language. Theoretical Grammar describes and explains peculiarities of the grammatical system of a language on the scientific basis.

There are several approaches to the study of the English language.

Traditional Grammar treats the nine parts of speech (nouns, verbs, adjectives, numerals, adverbs, pronouns, prepositions, conjunctions, and interjections) according to their formal features and functions in the sentence.

Thus, the word table belongs to the class of nouns, because it has the formal features of plurality (tables) and the possessive case (table's). Besides, it can function as a subject, predicative and object. Some words can belong to more than one part of speech. e. g. a) The room was decorated in yellow (noun). b) The yellow dress needed pressing (adjective). c) Dry cleaning will yellow that fabric (verb).

Structural Grammar treats the two types of meaning (lexical and structural) in the aspect of their influence on the meaning of the whole sentence. The lexical meaning is that registered in the dictionary. The structural meaning depends on the position in the sentence. Cf. e. g. The groby stils kraded mitly. This sentence has its structural meaning regardless the fact that all the words it is made up of have no dictionary meaning (except the). This meaning is 'several things of the same quality acted in a certain way'.

Transformational Grammar studies all possible sentences people are able to produce. In transformational Grammar all sentences are divided into basic (or kernel) and transformations. Transformations appear in the result of adding, deleting, or rearranging the words of a kernel sentence.

Grammar consists of two parts: morphology and syntax.

Morphology is traditionally defined as that part of grammar which studies morphemes and morphological structure of words.

Syntax is that branch of grammar which studies the syntactic functions of words and the syntactic structure of word combinations and sentences.

The traditional approach to the difference between morphology and syntax was based on the character of language units. Traditionally morphemes are always treated by morphology while sentences – by syntax. This approach is based on the assumption that we can always distinguish between words and phrases. Sometimes the borderline is not clearly cut. There are cases of overlapping. Thus, such combinations as will come, is reading can be studied in morphology where they are forms of words and equally in syntax where they are treated as free combinations of words. The problem turns to be even more complicated when we come across such combinations as is still reading.

Let's view the difference between morphology and syntax from another angle. Every grammatical unit has two types of relations: paradigmatic (in the system of language) and syntagmatic (established in speech). 

a) paradigmatic: those established in connection with other forms of the same units or between structurally homogenious elements united on the basis of possessing some common parts.

In other words, we find these relations when consider a language unit as part of the system. Thus it can be traced between the forms of one word (is reading, reads), or between the same forms of different words (e. g. reading, asking).

Forms of the type boy, boys, boy's, boys' have the same lexical meaning but different grammatical meanings. Thus, they constitute a lexeme. Word-forms of the type boys, children, people, men have the same grammatical meaning but different lexical meanings. They form a grammeme. Together they form a paradigm.

Paradigm is a unity of all lexemes and all grammemes of a given class of words.

We cannot observe paradigmatic relations in speech, they are systematic, thus often called "in absentia".

b) syntagmatic: those established in connection with other units of the same level.

In other words, we find these relations when consider a language unit in its surroundings . This may be found between morphemes in the structure of words, between words in the structure of a sentence, between concrete senten­ces in the structure of a complex syntactic unit.

Syntagmatic relations are typical of utterances, so they are often referred to as relations "in praesentia".

Structural approach to the difference between morphology and syntax is based on the character of relations: morphology studies paradigmatic relations, syntax studies syntagmatic connections.

Morphology seems to be more abstract than syntax since it studies forms extracted from their natural surroundings, it does not study actual ties between words in an utterance. On the other hand, morphology will not seem so abstract if we take into consideration the fact that it studies units which are very compact while syntax treats sentences which are naturally much larger units.

The spheres of morphology and syntax can change because all the language units enter both syntagmatic and paradigmatic relations. According to the new approach to the differentiation between morphology and syntax the former (morphology) should study both paradigmatic and syntagmatic relations of words, while the latter (syntax) should study paradigmatic and syntagmatic relations of sentences.