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Second-countable space — In topology, a second countable space, also called a completely separable space, is a topological space satisfying the second axiom of countability. A space is said to be second countable if its topology has a countable base. More explicitly,… … Wikipedia
second countable — adjective Having a countable base for its topology … Wiktionary
Countable set — Countable redirects here. For the linguistic concept, see Count noun. Not to be confused with (recursively) enumerable sets. In mathematics, a countable set is a set with the same cardinality (number of elements) as some subset of the set of… … Wikipedia
second violin — UK US noun [countable] [singular second violin plural second violins] music a musician who plays the violin in an orchestra and belongs to the group of violinists that is less important than the first violins … Useful english dictionary
Second-order logic — In logic and mathematics second order logic is an extension of first order logic, which itself is an extension of propositional logic.[1] Second order logic is in turn extended by higher order logic and type theory. First order logic uses only… … Wikipedia
second — ▪ I. second sec‧ond 1 [ˈsekənd] adjective second half/quarter/period ACCOUNTING the second half, quarter etc of the financial year: • The company expects second quarter sales to be substantially below those of the equivalent period a year ago.… … Financial and business terms
second — I UK [ˈsekənd] / US noun [countable] Word forms second : singular second plural seconds *** 1) a) an extremely short period of time that is one of the 60 parts in a minute She won the 400 metres race in 51 seconds. Each commercial lasts for 30… … English dictionary
second language — 1. a language learned by a person after his or her native language, esp. as a resident of an area where it is in general use. 2. a language widely used, esp. in educational and governmental functions in a region where all or most of its speakers… … Useful english dictionary
second home — UK / US noun [countable] Word forms second home : singular second home plural second homes 1) a house that someone owns but lives in only for short periods, for example holidays, not as their usual home 2) a place that you spend a lot of time in… … English dictionary
second cousin — UK / US noun [countable] Word forms second cousin : singular second cousin plural second cousins a child of your parent s cousin … English dictionary
