The three words in the headline for this post, and words derived from them—listed and defined below—stem from a common source.
Plan, plain, and plane all derive from the Latin adjective planus, meaning “clear,” “even,” “flat, level,” and “plain.”
Plan comes from the French word meaning “map”; the English word, originally a technical term in perspective drawing, soon came to apply to any diagram or drawing; usage was extended around the same time to refer to any set of details about a project or an event. The word also describes the action of preparing for a project or event. (A planform is the contour of a mass or object as seen from above.)
The adjectival use of plain stems from the Old French word meaning “even,” “flat,” and “smooth” and came also to mean “clear” or “evident” as well as “free from obstruction.” Later, additional senses of “ordinary,” “undecorated,” and “unattractive” joined those meanings. Idioms include “plain dealer,” meaning “one who is candid or honest,” “plain Jane,” for a woman of unprepossessing appearance, and “as plain as the nose on (one’s) face” as an expressive substitution for obvious. Plainclothes refers to a police officer in civilian clothing (plainclothesman was ubiquitous before female undercover police officers were common), someone who is plainspoken is frank, and a plainsong is a religious chant.
In Old French, plain also means “open countryside,” and it developed the sense of “level terrain” in English, originally in reference to Salisbury Plain. A floodplain is terrain built up by deposits of soil material caused by flooding or flat land susceptible to flooding.
To explain (the word, originally explane, literally means “make level”) is to make clear, but complain and complaint (and plaintive) are all unrelated, deriving from the Latin verb plangere, meaning “lament.”
Plane stems directly from Latin, and its use came about to distinguish what were originally both geometric and geographical senses of plain. Except for those who practice geometry or woodworking, it is best known as a truncation of airplane (originally aeroplane), which technically alludes to the aerodynamic wings of an aircraft rather than the entire structure. Biplane and triplane denote aircraft with two and three wings, respectively (generally stacked), not including smaller stabilizing wing structures. (Other specialized terms include seaplane and warplane.) To board a plane is to enplane (or emplane), exiting a plane is called deplaning.
In woodworking, a plane is a tool for smoothing surfaces, and to plane is to make level or smooth. As a verb, the word also denotes gliding or soaring or, in the case of a boat, skimming over the surface of water. (Hydroplane also serves for this meaning, especially in the context of powerboat racing, though the word also applies as a verb to any action of skimming over water.)
The name of the plane tree is unrelated, but planar means “two-dimensional” or “pertaining to a plane” and planaria is the designation for a genus of freshwater flatworms.
Here is another case of when I think that the word “plainclothesman” is suitable for both males and females, just like these other words:
airman, conman, craftsman, crewman, draftsman, fireman, fisherman, foreman, greensman, helmsman, junkman, linksman (someone who plays golf), manned, marksman, policeman, seaman, statesman, steersman, unmanned, yachtsman….
For example, with a new resident speaking, “Who is the congressman in this district?” Answer: “She is Dr. Susan Smith.”
“Someone get a policeman!” I am very happy when officer Barbara Bormann shows up soon with her badge and nightstick.
An unmanned aircraft or spacecraft does not have anyone it, male, female, or neuter.
An aircraft, spacecraft, or watercraft with just three women on board is manned, whether you like it or not. The three women could be the pilot, co-pilot, and navigator.
According to Merriam-Webster, a “greensman” is someone who decorates motion-picture sets with grass, flowers, shrubs, and other greenery. Good, almost anyone can do that work, with the right training. I thought that a greensman was someone who takes care of golf courses, and especially the greens, and this might be true, too.
There are other possibilities that are noncontrived: policewoman, plainclotheswoman, congresswoman, crewwoman, charwoman,
kinsman, kinswoman, saleswoman, saleslady, stateswoman. Horseman and horsewoman.
Other kinds of plainclothesmen, besides in undercover work. In most police jurisdictions, the detectives and administrators wear civilian clothing (usually business suits) rather than policeman’s uniforms. Just look at Sgt. Joe Friday of the TV show, “Dragnet”, Officer Bill Gannon of the same show, and the former chief-of-police Robert Ironside and his assistants of the TV show, “Ironside”, and the women of “Cagney and Lacey”. Most detectives are quite experienced policemen, and they carry ranks like “sergeant” and “lieutenant”. We saw the same kind of thing in the TV shows “CSI” = “Crime Scene Investigators”.
By the way, Carl Sagan recommended this kind of a TV program over 25 years ago. Dr. Sagan thought that the watchers might learn something about scientific methods from a program like CSI, and maybe some of them did.
In my case, I learned lots of science from “Star Trek”, “Sky King”, “The Undersea World of Jacques Cousteau”. For example, “Sky King” was the first place that I learned anything about cloud seeding.
You have neglected to mention a very important subject from high school. Most of us educators think that all college-bound students should study it. This is “Plane Geometry”, and it is the study of objects in the Euclidean plane. There is a key item that distinguishes plane geometry from all of the other kinds, and this is the Parallel Postulate (capitalized!).
Plane geometry leads us to the logical study of circles, triangles, quadrilaterals, parallelograms, regular polygons, and something that was mentioned is this column very recently: the Pythagorean Theorem (always capitalized in my book). Plane geometry leads us to trigonometry, and three items that I have always capitalized: the Law of Sines, the Law of Cosines, and the Law of Tangents.
Plane geometry leads to the study of areas, and eventually to integral calculus.
Plane geometry also leads us to the Cartesian plane, named for Rene Descartes, and the realm of “analytic geometry” and all of the (x, y) coordinates, and equations of lines, circles, and parabolas.
We should never leave out some things in the subject:
1) A few noteworthy newspapers in the U.S.A. named the “Plain Dealer”, with the most famous one being the “Cleveland Plain Dealer”.
2) A famous song that goes “The rain in Spain stays mainly in the plain!” (“By George, I think she’s got it!”)
3) Aeronautical terminology, with crucial words omitted: biplane, cargo plane, carrier plane, fighter plane, jet plane, land plane, mail plane, MONOPLANE, passenger plane, rocket plane, sailplane, scout plane, triplane, warplane, X-plane.
About the song “The Rain in Spain” – quoted from the Wikipedia:
“The song is a turning point in the plotline of the musical. Professor Higgins and Colonel Pickering have been drilling Eliza Doolittle incessantly with speech exercises, trying to break her Cockney accent and speech pattern. The key lyric in the song is “The rain in Spain stays mainly in the plain”, which contains five words that a Cockney would pronounce with [æɪ]or [aɪ] — more like “eye” — than the [usual pronunciation with the] diphthong [eɪ]. With the three of them nearly exhausted, Eliza finally “gets it”, and [she] recites the sentence with [five long As]. Then the trio breaks into song**, repeating this key phrase… [several times].
**Naturally — “My Fair Lady” is a musical.
There has to be a crucial song at a crucial moment, or more.
It is just like “Camelot”; “The Impossible Dream”; “76 Trombones”; “Don’t Cry for Me, Argentina”; “Oklahoma is O.K.”; “Mama Mia!”; and “Dancing Queen”.
My favorites from shows are all symphonic, and hence my heroes are John Williams, Elmer Bernstein, and Alexander Courage.
D.A.W.
“Planar” is a word that was devised in direct analogy to linear, angular, circular, globular, rectangular, and tubular. I do not think that “planar” is as old a word as the others are. Before that, people just used “flat” – “flach” in German.
All the same idea:
a bald-faced lie, a bare-faced like, a plain-faced lie, an open-faced lie.
Relevant to communications:
plain talk, plain language, plain English, plainsman, flatlander.
In cryptology, there are the important concepts of plaintext and ciphertext.
If a foe can capture a reasonable amount of plaintext, AND the corresponding ciphertext, then by working backwards, the foe could work out the encipherment (encryption) procedure. Next, this could be used for the decryption of future intercepted messages.
It is a continual “war of nerves” about who can keep secrets secure, and who can intercept and decipher secret messages. This is why the NSA has the nickname of “The Puzzle Palace”.