# Coherence

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
• 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

## 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