Many words are polysemous. There are two ways of handling this phenomenon in a semantic theory: One is full specification, where each meaning of a word is represented separately in the lexicon. The other is minimal specification, where one meaning of a word is considered to be central, and other meanings are derived from the central one. The article defends minimal specification by presenting a number of semantic transformations that can be used to generate new meanings. Firstly, parallels between the visual process and changes of meaning are outlined. It is argued that many types of semantic transformations can be analyzed as different forms of focusing. For example, metonymical transformations are parallel to zooming out(totem pro part) or zooming in(pars pro toto). The notion of a domain is discussed in relation to the theory of conceptual spaces. It is argued that metaphorical meaning changes can be analyzed as mappings between domains. The notion of a mapping becomes more precise when the geometric structures of the domains are considered. As a case study, some of the many meanings of 'over' are analyzed in terms of focusing or domain mappings. Finally, the productive functions of iterated semantic transformations are discussed.