The notion of macrostructure has been used in several disciplines in order to distinguish large-scale, or 'global' structures, from small-scale, or 'local' structures, that is, microstructure. The distinction between macrostructure and microstructure is relative to the perspective, aims or level of description: Macrostructures may again be seen as microstructures at a higher level of description, that is, in relation to even larger-scale macrostructures. For instance, the rooms of a house are microstructures relative to the overall, macrostructure of the house. But the house may again be a microstructure relative to the macrostructure of a neighborhood or a city, and so on. These differences of the level of description are also called differences of granularity: as is the case for photographs, fine-grained descriptions show more detail than coarse-grained ones. In linguistics and discourse analysis semantic macrostructures are the overall, global meanings of discourse, usually also described in terms of topic, gist, or upshot. These semantic macrostructures (global meanings or topics) are typically expressed in for instance the headlines and lead of a news report, or the title and the abstract of a scholarly article. Macrostructures of discourse are distinguished from its microstructures, that is, the local structures of words, clauses, sentences or turns in conversation. Macrostructures may be derived from microstructures by operations such as abstracting, that is, leaving out or summarizing specific details. Semantic macrostructures or topics define what is called the global coherence of discourse.