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[loo-sid] /ˈlu sɪd/
easily understood; completely intelligible or comprehensible:
a lucid explanation.
characterized by clear perception or understanding; rational or sane:
a lucid moment in his madness.
shining or bright.
clear; pellucid; transparent.
1575-85; < Latin lūcidus, equivalent to lūc-, stem of lūx light1 + -idus -id4
Related forms
lucidity, lucidness, noun
lucidly, adverb
nonlucid, adjective
nonlucidly, adverb
nonlucidness, noun
unlucid, adjective
unlucidly, adverb
unlucidness, noun
1. plain, understandable, evident, obvious. 2. sound, reasonable. 3. radiant, luminous. 4. limpid.
1, 4. obscure. 2. irrational. 3. dim. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for lucid
  • The moonlight, which seems so lucid and brilliant when you look up, is all pearl and smoke round the pond and the hills.
  • Although the grant has been renewed, the best efforts of the few lucid participants have met only cold rebuke.
  • It's taken years, and in her more lucid moments, she's not even there yet.
  • Every successive crisis finds him as understanding of others as he is lucid about himself, and his impulse is truly magnanimous.
  • They are lucid, they get all their laughs, but the price of their cultivation is an unfortunate absence of urgency.
  • In a private, lucid moment, he might have conceded this disproportion.
  • It's a bit jarring to see a lucid pro-transparency, pro-security argument from a federal prosecutor.
  • He insisted he was perfectly alert and lucid, adding that he was not a publicity hound, either.
  • These serve as a lucid introduction to the theory and practice of development.
  • lucid prose and vivid examples make the book admirably accessible to non-specialists.
British Dictionary definitions for lucid


readily understood; clear
shining or glowing
(psychiatry) of or relating to a period of normality between periods of insane or irresponsible behaviour
Derived Forms
lucidity, lucidness, noun
lucidly, adverb
Word Origin
C16: from Latin lūcidus full of light, from lūx light
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for lucid

1590s, "bright, shining," from Latin lucidus "light, bright, clear," figuratively "perspicuous, lucid, clear," from lucere "to shine," from lux (genitive lucis) "light," from PIE root *leuk- "to shine, be bright" (see light (n.)). Sense of "easy to understand" first recorded 1786. Lucid interval "period of calm or temporary sanity" (1580s) is from Medieval Latin lucida intervalla (plural), which was common in medieval English legal documents (cf. non est compos mentis, sed gaudet lucidis intervallis). Related: Lucidly; lucidness (1640s).

Online Etymology Dictionary, © 2010 Douglas Harper
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lucid in Technology

1. Early query language, ca. 1965, System Development Corp, Santa Monica, CA. [Sammet 1969, p.701].
2. A family of dataflow languages descended from ISWIM, lazy but first-order.
Ashcroft & Wadge , 1981.
They use a dynamic demand driven model. Statements are regarded as equations defining a network of processors and communication lines, through which the data flows. Every data object is thought of as an infinite stream of simple values, every function as a filter. Lucid has no data constructors such as arrays or records. Iteration is simulated with 'is current' and 'fby' (concatenation of sequences). Higher-order functions are implemented using pure dataflow and no closures or heaps.
["Lucid: The Dataflow Language" by Bill Wadge wwadge@csr.UVic.CA and Ed Ashcroft, c. 1985]. ["Lucid, the Dataflow Programming Language", W. Wadge, Academic Press 1985].
The Free On-line Dictionary of Computing, © Denis Howe 2010
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