[koh-heer-uhns, -her-]
the act or state of cohering; cohesion.
logical interconnection; overall sense or understandability.
congruity; consistency.
Physics, Optics. (of waves) the state of being coherent.
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 cohesion ( def 4 ).
Also, coherency.

1570–80; coher(ent) + -ence

noncoherence, noun
noncoherency, noun

3. correspondence, harmony, agreement, rationality. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
coherence or coherency (kəʊˈhɪərəns, kəʊˈhɪərənsɪ)
1.  logical or natural connection or consistency
2.  another word for cohesion
coherency or coherency

Collins English Dictionary - Complete & Unabridged 10th Edition
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Word Origin & History

c.1580, from cohérence (16c.), from L. cohærentia, noun of state from cohærentem (see coherent).
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Science Dictionary
coherence   (kō-hîr'əns, -hěr'-)  Pronunciation Key 
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.
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Encyclopedia Britannica


a fixed relationship between the phase of waves in a beam of radiation of a single frequency. Two beams of light are coherent when the phase difference between their waves is constant; they are noncoherent if there is a random or changing phase relationship. Stable interference patterns are formed only by radiation emitted by coherent sources, ordinarily produced by splitting a single beam into two or more beams. A laser, unlike an incandescent source, produces a beam in which all the components bear a fixed relationship to each other

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
There seems to be little coherence in the jurist's volte-face.
Other things can be taught, so that the students can write with ease and
Their unification should bring more coherence to anti-poverty programmes.
He figured out that they were all the same thing and helped bring coherence to
  a rambling tale.
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