Words put together to form lexical units make phrases or word-groups. The largest two-facet lexical unit comprising more than one word is the word-group observed on the syntagmatic level of analysis. The degree of structural and semantic cohesion of word-groups may vary. Functionally and semantically inseparable word-groups like at least, point of view, by means of, take place are phraseological units. Semantically and structurally more independent word-groups a week ago, man of wisdom, take lessons, kind to people are defined as free or variable word-groups or phrases. To get a better insight into the essentials of structure and meaning of word-groups we must begin with a brief survey of the main factors active in uniting words into word-groups. The two main linguistic factors to be considered in uniting words into word-groups are: 1) the lexical valency of words 2) the syntactic valency of words.