The word «polysemy» means «plurality of meanings» it exists only in the language, not in speech. A word which has more than one meaning is called polysemantic.
Different meanings of a polysemantic word may come together due to the proximity of notions which they express. E.g. the word «blanket» has the following meanings: a woolen covering used on beds, a covering for keeping a horse warm, a covering of any kind /a blanket of snow/, covering all or most cases /used attributively/, e.g. we can say «a blanket insurance policy».
Yet, the general tendency with English vocabulary at the modern stage of its history is to increase the total number of its meanings in this way to provide for a quantitative and qualitative growth of the language’s expressive resources. The semantic structure of a polysemantic word is treated as a system of meanings. For example, the semantic structure of the noun fire could be roughly presented by this scheme(only the most frequent meanings are given)
Fire, n. - I flame- II instance of destructive burning (e.g. a forest fire); - III burning materials in a stove, fire-place (e.g. There is a fire in the next room. A camp fire); - IV shooting of guns (e.g. to open/case fire); - V strong feeling, passion, enthusiasm (e.g. a speech lacking fire)
