Coherence

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:

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.

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
 * Cohere, a Canadian natural language processing software developer
 * Sense of coherence, a construct in the health theory salutogenesis