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 coherent system of units is a system of units of measurement used to express physical quantities that are defined in such a way that the equations relating the numerical values expressed in the units of the system have exactly the same form, inc ...

, 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 For an electromagnetic wave, the coherence time is the time over which a propagating wave (especially a laser or maser beam) may be considered coherent, meaning that its phase is, on average, predictable. In long-distance transmission systems, ...

, 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) In a thought experiment proposed by the Italian probabilist Bruno de Finetti in order to justify Bayesian probability, an array of wagers is coherent precisely if it does not expose the wagerer to certain loss regardless of the outcomes of events ...

, a concept in Bayesian statistics *

Coherence (signal processing) In signal processing, the coherence is a statistic that can be used to examine the relation between two signals or data sets. It is commonly used to estimate the power transfer between input and output of a linear system. If the signals are ergodi ...

, 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 mathematics, and particularly category theory, a coherence condition is a collection of conditions requiring that various compositions of elementary morphisms are equal. Typically the elementary morphisms are part of the data of the category ...

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 In mathematics, especially in algebraic geometry and the theory of complex manifolds, coherent sheaves are a class of sheaves closely linked to the geometric properties of the underlying space. The definition of coherent sheaves is made with ref ...

, 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) Coherence, also called uniformity or consistency, is a criterion for evaluating rules for fair division. Coherence requires that the outcome of a fairness rule is fair not only for the overall problem, but also for each sub-problem. Every part of ...

, a consistency requirement of fair division rules.

Philosophy

Coherentism In philosophical epistemology, there are two types of coherentism: the coherence theory of truth; and the coherence theory of justification (also known as epistemic coherentism). Coherent truth is divided between an anthropological approach, wh ...

, philosophical theories in modern epistemology, the study of knowledge *

Coherence theory of truth Coherence theories of truth characterize truth as a property of whole systems of propositions that can be ascribed to individual propositions only derivatively according to their coherence with the whole. While modern coherence theorists hold that ...

, a theory which regards truth as coherence within some specified set of sentences, propositions or beliefs

Computer science

Coherence (programming language) Subtext is a moderately visual programming language and environment, for writing application software. It is an experimental, research attempt to develop a new programming model, called Example Centric Programming, by treating copied blocks as fi ...

, an experimental programming language based upon Subtext * Cache coherence, a special case of memory coherence *

Memory coherence Memory coherence is an issue that affects the design of computer systems in which two or more processors or cores share a common area of memory. In a uniprocessor system (whereby, in today's terms, there exists only one core), there is only one p ...

, 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) Coherent is a clone of the Unix operating system for IBM PC compatibles and other microcomputers, developed and sold by the now-defunct Mark Williams Company (MWC). Historically, the operating system was a proprietary product, but it became open ...

, a UNIX-clone operating system *

Oracle Coherence In computing, Oracle Coherence (originally Tangosol Coherence) is a Java-based distributed cache and in-memory data grid. It is claimed to be "intended for systems that require high availability, high scalability and low latency, particularly in ...

, an in-memory data grid product from Oracle

Other uses

* Coherence (cognitive science), a property of mental/cognitive states *

Coherence (linguistics) Coherence in linguistics is what makes a text semantically meaningful. It is especially dealt with in text linguistics. Coherence is achieved through syntactical features such as the use of deictic, anaphoric and cataphoric elements or a logic ...

, what makes a text semantically meaningful * Coherence (music theory), a synonym for strict Rothenberg propriety in diatonic set theory *

Coherent optical module Coherent optical module refers to a typically hot-pluggable coherent optical transceiver that uses coherent modulation (BPSK/QPSK/ QAM) rather than amplitude modulation (RZ/ NRZ/ PAM4) and is typically used in high-bandwidth data communications appl ...

, 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 the fields of actuarial science and financial economics there are a number of ways that risk can be defined; to clarify the concept theoreticians have described a number of properties that a risk measure might or might not have. A coherent ris ...

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