set of rational numbers
21Dyadic rational — Dyadic rationals in the interval from 0 to 1. In mathematics, a dyadic fraction or dyadic rational is a rational number whose denominator is a power of two, i.e., a number of the form a/2b where a is an integer and b is a natural number; for… …
22Nested set model — The nested set model is a particular technique for representing nested sets (also known as trees or hierarchies) in relational databases. The term was apparently introduced by Joe Celko; others describe the same technique without naming it [1] or …
23Mandelbrot set — Initial image of a Mandelbrot set zoom sequence with a continuously coloured environment …
24Paradoxes of set theory — This article contains a discussion of paradoxes of set theory. As with most mathematical paradoxes, they generally reveal surprising and counter intuitive mathematical results, rather than actual logical contradictions within modern axiomatic set …
25Clopen set — In topology, a clopen set (a portmanteau of closed open set) in a topological space is a set which is both open and closed. That this is possible for a set is not as counter intuitive as it might seem if the terms open and closed were thought of… …
26Dense set — In topology and related areas of mathematics, a subset A of a topological space X is called dense (in X) if any point x in X belongs to A or is a limit point of A.[1] Informally, for every point in X, the point is either in A or arbitrarily close …
27Morse–Kelley set theory — In the foundation of mathematics, Morse–Kelley set theory (MK) or Kelley–Morse set theory (KM) is a first order axiomatic set theory that is closely related to von Neumann–Bernays–Gödel set theory (NBG). While von Neumann–Bernays–Gödel set theory …
28Negative and non-negative numbers — A negative number is a number that is less than zero, such as −2. A positive number is a number that is greater than zero, such as 2. Zero itself is neither positive nor negative. The non negative numbers are the real numbers that are not… …
29Meagre set — In the mathematical fields of general topology and descriptive set theory, a meagre set (also called a meager set or a set of first category) is a set that, considered as a subset of a (usually larger) topological space, is in a precise sense… …
30Gaussian rational — In mathematics, a Gaussian rational number is a complex number of the form p + qi, where p and q are both rational numbers. The set of all Gaussian rationals forms the Gaussian rational field, denoted Q(i), obtained by adjoining the… …
