Words put together to form lexical units make phrases or word-groups. One must recall that lexicology deals with words, word-forming morphemes and word-groups.
The degree of structural and semantic cohesion of word-groups may vary. Some word-groups, e.g. at least, point of view, by means, to take place, etc. seem to be functionally and semantically inseparable. They are usually described as set phrases, word-equivalents or phraseological units and are studied by the branch of lexicology which is known as phraseology. In other word-groups such as to take lessons, kind to people, a week ago, the component-members seem to possess greater semantic and structural independence. Word-groups of this type are defined as free word-groups or phrases and are studied in syntax.
Before discussing phraseology it is necessary to outline the features common to various word-groups irrespective of the degree of structural and semantic cohesion of the component-words.
There are two factors which are important in uniting words into word-groups:
- the lexical valency of words;
- the grammatical valency of words.
Lexical valency.
Words are used in certain lexical contexts, i.e. in combinations with other words. E.g. the noun question is often combined with such adjectives as vital, pressing, urgent, delicate, etc. This noun is a component in a number of other word-groups: to raise a question (not to lift), a question of the hour - àêòóàëüíûé âîïðîñ, çëîáîäíåâíûé âîïðîñ.
The aptness of a word to appear in various combinations is described as its lexical valency. The range of the lexical valency of words is delimited by the inner structure of the English words. Thus, to raise and to lift are synonyms, but only the former is collocated with the noun question. The verbs to take, to catch, to seize, to grasp are synonyms, but they are found in different collocations:
to take - exams, measures, precautions, etc.;
to grasp - the truth, the meaning.
Words habitually collocated in speech tend to form a cliche.
The lexical valency of correlated words in different languages is not identical, because as it was said before, it depends on the inner structure of the vocabulary of the language. Both the English flower and the Russian öâåòîê may be combined with a number of similar words, e.g. garden flowers, hot house flowers (cf. the Russian - ñàäîâûå öâåòû, îðàíæåðåéíûå öâåòû), but in English flower cannot be combined with the word room, while in Russian we say êîìíàòíûå öâåòû (in English we say pot-flowers).
Grammatical valency.
Words are also used in grammatical contexts. The minimal grammatical context in which the words are used to form word-groups is usually described as the pattern of the word-group. E.g., the adjective heavy can be followed by a noun (A+N) - heavy food, heavy storm, heavy box, heavy eater. But we cannot say "heavy cheese " or "heavy to lift, to carry", etc.
The aptness of a word to appear in specific grammatical (or rather syntactical) structures is termed grammatical valency.
The grammatical valency of words may be different. The grammatical valency is delimited by the part of speech the word belongs to. E.g., no English adjective can be followed by the finite form of a verb.
Then, the grammatical valency is also delimited by the inner structure of the language. E.g., to suggest, to propose are synonyms. Both can be followed by a noun, but only to propose can be followed by the infinitive of a verb — to propose to do something.
Clever and intelligent have the same grammatical valency, but only clever can be used in word-groups having the pattern A+prep+N - clever at maths.