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lucid

/ˈluːsɪd//ˈluːsɪd/·adjective
clear and easy to understand; thinking or expressed with clarity
Fig. 1 — I watch a pool gone to glass: the surface lies dead still, and on the bottom every stone and a small fish show in full colour and detail, as crisp as if there were no water at all.
01Definition

Lucid prose lets the idea shine straight through, as if the words were glass — the Latin lucidus means 'full of light'. A lucid explanation makes a hard subject feel easy; a lucid argument is coherent enough to follow on the first reading. Applied to the mind it means clear-headed: a feverish patient may have a brief lucid interval before the confusion returns. What is lucid is never ambiguous, because light leaves nowhere for doubt to hide.

02In use
  • iHer lecture was so lucid that even the most abstract proof felt obvious.
  • iiHe has a gift for lucid writing: complex policy explained without a single confusing sentence.
  • iiiAfter hours of fever she had a lucid moment, recognized her daughter, then drifted off again.
03Collocations
  • a lucid explanation
  • lucid prose
  • a lucid account
  • a lucid interval

Family lucidity (noun) · lucidly (adverb)

04Relations

=clear, coherent, intelligible, articulate, transparent

≠ambiguous, confusing, muddled

05Compared
PairThe difference
lucid vs ambiguousclear on the first reading → lucid; honestly supports two meanings → ambiguous ('LOO-sid').
lucid vs vividclear to the mind — prose, argument, thought → lucid; alive to the senses — image, memory, colour → vivid.
06TOEFL & IELTS

A strong word for both exams. TOEFL reading praises authors for 'lucid' explanations, and vocabulary items pair it with 'clear'. In IELTS Speaking and Writing, calling an argument 'lucid' (or writing 'lucidly') signals high lexical resource — just keep it for genuine clarity, not mere brevity. Note the noun 'lucidity' and the medical set phrase 'a lucid interval'.

07Asked
Why is it called lucid dreaming?
Because the dreamer's mind is lucid — clear and aware — while the dream runs: you know you are dreaming as it happens. The term was coined by the Dutch psychiatrist Frederik van Eeden in 1913, and it borrows the word's mental sense (a lucid mind), not the stylistic one. The dream itself may be pure chaos; what is lucid is you.
What is a lucid interval?
A temporary return of clarity inside a longer confusion. Medicine uses it for the deceptive calm after some head injuries, when a patient briefly seems fine, and for windows of clear-headedness in fever or dementia. Law has long used it too: a will signed during a lucid interval can stand, because capacity existed at that moment. Both uses trust the same idea — clarity that visits rather than stays.
Does lucid describe clear thinking or clear explanation?
Both, and the root holds them together: Latin lucidus, 'full of light'. A lucid mind sees clearly; lucid prose lets readers see clearly. The scene above is careful about what that clarity is — nothing is added or switched on; the water only goes still, and the bottom appears. That is the word's promise in either use: no obstacle left between the thing and the eye.
What is the opposite of lucid?
Ambiguous, when the failure is in the message, and muddled or confused, when it is in the mind — lucid and its chief opposite face off, scene against scene, on the lucid vs ambiguous page in the 'Compared' list above.
Which English words share lucid's root?
The Latin lux/luc- 'light' family is large: translucent (light passes through), elucidate (to shed light on — to explain), lucent (glowing), and the name Lucia. Elucidate is the useful cousin for essays: where lucid describes the writing, elucidate is what the writing does to its subject. Even lucid dreaming keeps the metaphor — awareness as a light left burning inside sleep.