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According to the narrow and broad understanding of periphrasis and synonyms, which relies on the representative function of language, it is necessary to take into account the cognitive factors that determine the relationship between the nominating word (periphrasisable concept) and the periphrasing concept. As exemplified in the names of celestial bodies there is tendency of periphrasis and synonym, but not the rules. Opportunity of duplicate use of the words “moon” and “month” shows semantic opposition. Meanwhile in language there are non-stylistic periphrases for celestial object. In a broad sense periphrases and synonyms are considered as stylistic synonyms. These features focus attention of the linguistic personality and allow allocating a specific descriptive feature in the periphrasis image. Periphrasis is more voluminous, wider in its content due to the presence of certain structural components or the presence of associative features.
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We prove that in the narrow sense periphrastic names cannot be considered as a simple synonymous replacement of the word-nominee, since the meaning of the periphrase is not identical with the meaning of the word-nominee.
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We consider the ability of language to express identical content by periphrastic means that reflects in the periphrase and synonym ratio.
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