{{Broad-concept article}}{{wiktionary|coherence|coherency|coherent|incoherence|incoherent}}

Coherence is, in general, a state or situation in which all the parts or ideas fit together well so that they form a united whole.

More specifically, '''coherence''', '''coherency''', or '''coherent''' may refer to the following:

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== Physics ==

* Coherence (physics), an ideal property of waves that enables stationary (i.e. temporally and spatially constant) interference * Coherence (units of measurement), a derived unit that, for a given system of quantities and for a chosen set of base units, is a product of powers of base units with no other proportionality factor than one * Coherence time, the time over which a propagating wave (especially a laser or maser beam) may be considered coherent; the time interval within which its phase is, on average, predictable

== Mathematics ==

* Coherence (philosophical gambling strategy), a concept in Bayesian statistics * Coherence (signal processing), a statistic that can be used to examine the relation between two signals or data sets * Coherence (statistics), a property of self-consistency across a set of assessments, or the strength of association between two series * Coherence condition in category theory, a collection of conditions requiring that various compositions of elementary morphisms are equal * Coherency (homotopy theory) in homotopy theory and (higher) category theory * Coherent sampling, a relationship used in Fast Fourier transforms * Coherent set of characters in representation theory, a property of sets of characters that allows one to extend an isometry from the degree-zero subspace of a space of characters to the whole space * Coherent sheaf, a specific class of sheaves having particularly manageable properties closely linked to the geometrical properties of the underlying space * Mutual coherence (linear algebra), sometimes referred to as coherence, the maximum absolute value of the cross-correlations between the columns of a matrix * Multi-spectral phase coherence, a generalized nonlinear cross-frequency phase coupling metric introduced by Yang et al., 2016 * Coherence (fairness), a consistency requirement of fair division rules. * Coherent topology, topology determined by a family of subspaces.

== Philosophy ==

* Coherentism, philosophical theories in modern epistemology, the study of knowledge * Coherence theory of truth, a theory which regards truth as coherence within some specified set of sentences, propositions or beliefs

== Computer science == * Coherence (programming language), an experimental programming language based upon Subtext * Cache coherence, a special case of memory coherence * Memory coherence, a concept in computer architecture * In scrum and agile methodologies, coherence is defined as a measure of the relationships between backlog items which make them worthy of consideration as a whole.

=== IT products === * Coherence (software), a component of Parallels Desktop for Mac, the Windows virtualization software * Coherent (operating system), a UNIX-clone operating system * Oracle Coherence, an in-memory data grid product from Oracle

== Other uses ==

* Coherence (cognitive science), a property of mental/cognitive states * Coherence (linguistics), what makes a text semantically meaningful * Coherence (music theory), a synonym for strict Rothenberg propriety in diatonic set theory * Coherent optical module, a hot-pluggable optical transceiver implementing a coherent modulation algorithm * Coherence time (communications systems), duration when a communication channel can be assumed to be constant * Coherent, Inc., a company specializing in equipment to make and measure coherent light (lasers) * Coherent risk measure in financial economics, a function that satisfies properties of monotonicity, sub-additivity, homogeneity, and translational invariance * ''Coherence'' (film), a 2013 science fiction film by James Ward Byrkit * Sense of coherence, a construct in the health theory salutogenesis * Policy coherence for development, a concept in development cooperation

== See also ==

* Cohesion (disambiguation) * Mutual coherence (disambiguation) * {{Lookfrom|coherence}} * {{Lookfrom|coherent}}

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