Lucid
adjective
Clearly expressed and simple to understand; straightforward
Able to think and express rationally and intelligently; mentally stable
Transparent to light; shining with transmitted light
Usage
Leaning over the side of a boat, you spot something incredible on the sandy bottom of the lake. You rub your eyes, but there's no need. The water is so lucid, so crystal-clear that you can see everything in its depths with no problem - including the mesmerizing, diaphanous mermaid smiling up at you lazily. Your heartbeat accelerates as your imagination fills with pirates and treasure and swashbuckling swordfights. You eagerly call to your first-mate, but by the time he arrives you're babbling incoherently; in your excitement, you're anything but lucid. Luckily, your first-mate has much more presence of mind, and he's able to calmly and lucidly point out that your new underwater friend is just a lost pool toy.
To further elucidate: lucid is an adjective that usually describes something as clear and extremely easy to understand. This usage often characterizes spoken or written messages that are well expressed and logical. A lucid instruction manual, for example, would be easy to read and follow, and lucid word choices would communicate your point sensibly and eloquently. To paraphrase an old cliché, lucid expressions and progressions are simple, sweet, and to the point.
It’s easiest to come up with articulate explanations when you're thinking straight; it makes sense, then, that lucid also frequently characterizes a person as thinking clearly or as mentally balanced. Those who are lucid in this sense are understood to be totally in their right minds, perhaps despite the presence of outside stressors or the craziness of others. This usage implies that someone is calm yet alert, able to look at a problem rationally and objectively before coming up with an intelligent response. Essentially, their thoughts are moving as smoothly and logically as a swift, crystalline stream of water. Similarly, lucid also sometimes specifically indicates that someone is mentally healthy or else experiencing a period of reason in the midst of insanity.
Finally, lucid can more literally refer to something as transparent to light. This usage might imply that an object is perfectly clear, like a soap bubble that you can completely see through, or actually luminous by dint of the light flowing through it, like a gemstone that seems to glow under a lamp. You're most likely to see this type of lucid applied to bodies of water or crystalline materials, but it occasionally pops up in more creative descriptions of gleaming or translucent objects. You could always try to impress dates by telling them you're basking in the glow of their lucid eyes (results may vary).
Example: Professor Gordon's goal was to write a textbook about particle physics that would be lucid to everyone.
Example: Assuming that particle physics could be made lucid to anyone proved Professor Gordon to be far from lucid himself.
Example: Seeing that the first draft of the opening chapter was anything but lucid, Professor Gordon's editor realized that he was in for a cloudy week.
Example: Remarkably, Professor Gordon was always far more lucid while in the field - something about the particle accelerator helped him think more clearly.
Example: Even the most lucid of microscope lenses can't reveal the tiny quark.
Example: Professor Gordon's desk was illuminated beneath a lucid window.
Origin
Although the most common uses of lucid today refer to things that are easily comprehendible, the word's secondary English meaning of "filled with light" is actually older. This is easy to understand when you consider lucid's earliest predecessor, the Proto-Indo-European root luek-, meaning "to emit light." This would inspire the Latin (almost everything goes through Latin) verb lucere, which also meant "to emit light." From this would come the derivative adjective lucidus, which, as the first five letters make perfectly clear, meant either "bright or transparent to light" or "clear and understandable." Lucid has been used in English to describe things as "radiant" or "agleam" since the 1590s. The word's metaphorical, and now more common, sense was first recorded in the mid-1780s.
Derivative Words
Lucidly: This adverb is used to characterize an action, adjective, or other adverb as displaying or related to clarity and rational thinking. It can also describe an action, adjective, or adverb as being a result of luminescence or transparency.
Example: The poet's voice rang out lucidly as he recited his latest work.
Example: The poem's intriguing message made Mary feel lucidly thoughtful.
Example: The moonlight danced lucidly across the car mirrors.
Lucidness: This noun can be used either literally or figuratively to refer to the quality of clearness or luminosity.
Example: The reporter's lucidness helped even those who were just turning on the news figure out what was happening.
Example: I saw myself reflected off the surface of the water in perfect lucidness.
Lucidity: Although this alternate noun form can fit in any situation you'd find lucidness, it also has a couple of meanings that are all its own. Medically speaking, lucidity is another way of saying sanity; psychiatrists and other doctors look for it when trying to determine if a patient is in the right mind to make decisions. Occasionally, lucidity can also refer to the possession of supernatural mental powers like being able to see the future or into other dimensions. Lucidity is pluralized as lucidities.
Example: My inability to put together what had appeared to be a simple end table had me questioning my own lucidity.
Example: If I had had the lucidity to foresee that this would be so frustrating, I wouldn't have bought the stupid kit in the first place.
Example: In the end, I lamely blamed my failure on the lack of lucidity of the instruction manual.
Similar Words
Pellucid is a somewhat uncommon word that, in addition to meaning "easy to follow" and "limpid," can describe things that perfectly reflect light (like a shiny, pellucid mirror). Another similar word, lucent, shares lucid's literal definitions of "transparent" and "aglow with transmitted light," but isn't used at all to indicate the clarity of a message or of someone's mind.
Actually, lucid might remind you of a lot of familiar words related to light, such as translucent, luminous, illuminate, and luminosity. All share the stressed syllable lu-, indicating their ancient connection to the Proto-Indo-European root luek, meaning "to emit light."
Finally, we'd like to shed a little light on the verb elucidate, meaning "to explain in a way that is easy to grasp." Elucidate isn't a derivative of the English lucid, but it does come from one of that word's more recent predecessors: lucidus, which meant "shining with light." You can think of elucidating something as shining a light on it so that its meaning is easy to see.
In Literature
From Gabriel Garcia Márquez' Love in the Time of Cholera:
Without intending to, without even knowing it, he demonstrated with his life that his father had been right when he repeated until his dying day that there was no one with more common sense, no stonecutter more obstinate, no manager more lucid or dangerous, than a poet.
Lucid here characterizes poets as clear-thinking and entirely logical. The catch, though, is that poets' logic comes from their romantic ways of viewing the world. This explains how Florentino Ariza - the "he" referenced and the novel's protagonist - can be completely coherent and lucid while at the same time chasing an impossible ideal.
In Pop Culture
Lucid has clearly left its mark on the imaginations of English speakers, since it serves as the name of a programming language, an American Naval minesweeper that served two tours in Vietnam, and an award-winning Canadian movie.
Comments
If you trawl around psychology videos on YouTube for long enough, you'll soon hear about the phenomenon of lucid dreaming. In lucid dreams, dreamers are actually aware that they're dreaming, and as a result have full control of their thoughts. This allows them to (theoretically) control the dream; they can change the setting to whatever they want and do crazy things like fly and ride unicorns. As cool as lucid dreaming sounds, it takes quite a bit of practice and discipline to accomplish.
Mnemonic
Sanity: use it or (you won't be) lucid
Lucid is as clear liquid
Tags
Fluid, Light, Transparent, Clear, Pellucid
Bring out the linguist in you! What is your own interpretation of lucid. Did you use lucid in a game? Provide an example sentence or a literary quote.