Coherence

[koh-heer-uh ns, -her-] /koʊˈhɪər əns, -ˈhɛr-/

noun
1.
the act or state of ; .
2.
logical interconnection; overall sense or understandability.
3.
congruity; consistency.
4.
Physics, Optics. (of waves) the state of being .
5.
Linguistics. the property of unity in a written text or a segment of spoken discourse that stems from the links among its underlying ideas and from the logical organization and development of its thematic content.
Compare (def 4).
/kəʊˈhɪərəns/
noun
1.
logical or natural connection or consistency
2.
another word for cohesion (sense 1)
n.

late 16c., from Middle French cohérence (16c.), from Latin cohaerentia, noun of state from cohaerentem (see coherent). Related: Coherency.
coherence
(kō-hîr’əns, -hěr’-)
A property holding for two or more waves or fields when each individual wave or field is in phase with every other one. Lasers, for example, emit almost perfectly coherent light; all the photons emitted by a laser have the same frequency and are in phase. Since quantum states can be described by a wave equation, coherence can hold for quantum states in general, though only among bosons. Coherence is generally possible in physical systems that may undergo superposition. Maintaining coherence of light is important in fiber optic communications. See also Bose-Einstein condensate.