plain

Etymology 1

From Middle English pleyn, borrowed from Anglo-Norman pleyn, playn, Middle French plain, plein, and Old French plain, from Latin plānus (“flat, even, level, plain”).

adj

1. (now rare, regional) Flat, level.
2. Simple, unaltered.
   1. Ordinary; lacking adornment or ornamentation; unembellished.
      He was dressed simply in plain black clothes.
      a plain tune
      The ability of a segment of a glass sphere to magnify whatever is placed before it was known around the year 1000, when the spherical segment was called a reading stone, essentially what today we might term a frameless magnifying glass or plain glass paperweight. 2013 September–October, Henry Petroski, “The Evolution of Eyeglasses”, in American Scientist
   2. Of just one colour; lacking a pattern.
      a plain pink polycotton skirt
   3. Simple in habits or qualities; unsophisticated, not exceptional, ordinary.
      They're just plain people like you or me.
      plain yet pious Christians 1654, Henry Hammond, Of Fundamentals
      the plain people 1861, Abraham Lincoln, Message to Congress in Special Session, July 4th
   4. (of food) Having only few ingredients, or no additional ingredients or seasonings; not elaborate, without toppings or extras.
      Would you like a poppy bagel or a plain bagel?
   5. (computing) Containing no extended or nonprinting characters (especially in plain text).
3. Obvious.
   1. Evident to one's senses or reason; manifest, clear, unmistakable.
   2. Downright; total, unmistakable (as intensifier).
      His answer was just plain nonsense.
4. Open.
   1. Honest and without deception; candid, open; blunt.
      Let me be plain with you: I don't like her.
      [VV]e are able with playne demonſtration to proue, and vvith reaſon to perſvvade that in tymes paſt our fayth vvas alike, that then vve preached thinges correſpondent vnto the forme of faith already published of vs, ſo that none in this behalfe can repyne or gaynesay vs. 1577, Socrates Scholasticus [i.e., Socrates of Constantinople], “Constantinus the Emperour Summoneth the Nicene Councell, it was Held at Nicæa a Citie of Bythnia for the Debatinge of the Controuersie about the Feast of Easter, and the Rootinge out of the Heresie of Arius”, in Eusebius Pamphilus, Socrates Scholasticus, Evagrius Scholasticus, Dorotheus, translated by Meredith Hanmer, The Avncient Ecclesiasticall Histories of the First Six Hundred Yeares after Christ, Wrytten in the Greeke Tongue by Three Learned Historiographers, Eusebius, Socrates, and Euagrius. …, book I (The First Booke of the Ecclesiasticall Historye of Socrates Scholasticvs), imprinted at London: By Thomas Vautroullier dwelling in the Blackefriers by Ludgate, →OCLC, page 225
   2. Clear; unencumbered; equal; fair.
      Our troops beat an army in plain fight. 1711, Henry Felton, Dissertation on Reading the Classics
5. Not unusually beautiful; unattractive.
   Yet her beauty clung to her like an identity she was trying to deny and her plainness kept slipping like a bad disguise. 1986, John le Carré, A Perfect Spy
   Throughout high school she worried that she had a rather plain face.
6. (card games) Not a trump.

adv

1. (colloquial) Simply.
   It was just plain stupid.
   I plain forgot.
2. (archaic) Plainly; distinctly.
   Tell me plain: do you love me or no?

Etymology 2

From Anglo-Norman plainer, pleiner, variant of Anglo-Norman and Old French pleindre, plaindre, from Latin plangere, present active infinitive of plangō.

noun

1. (rare, poetic) A lamentation.
   The warrior-threat, the infant's plain, The mother's screams, were heard in vain; 1815, Sir Walter Scott, The Lady of the Isles, Canto IV, part IX

verb

1. (reflexive, obsolete) To complain.
2. (transitive, intransitive, now rare, poetic) To lament, bewail.
   to plain a loss
   Thy mother could thee for thy cradle set Her husband's rusty iron corselet; Whose jargling sound might rock her babe to rest, That never plain'd of his uneasy nest.
   Then came I crying, and to-day, / With heavier cause to plain, / Depart I into death away, / Not to be born again. 1936, Alfred Edward Housman, More Poems, "XXV", lines 5–9

Etymology 3

From Old French plain, from Latin plānum (“level ground, a plain”), neuter substantive from plānus (“level, even, flat”). Doublet of llano, piano, and plane.

noun

1. An expanse of land with relatively low relief, usually exclusive of forests, deserts, and wastelands.
   1961, J. A. Philip. Mimesis in the Sophistês of Plato. In: Proceedings and Transactions of the American Philological Association 92. p. 467. For Plato the life of the philosopher is a life of struggle towards the goal of knowledge, towards “searching the heavens and measuring the plains, in all places seeking the nature of everything as a whole”
2. (archaic) Synonym of field in reference to a battlefield.
   You have stormed no town and found the money there ; neither did you find it in the plains of Plassey after the defeat of the Nawab 1899, Alexander John Arbuthnot, Lord Clive: The Foundation of British Rule in India
3. (obsolete) Alternative spelling of plane: a flat geometric field.

verb

1. (obsolete, transitive) To level; to raze; to make plain or even on the surface.
   We would rake Europe rather, plain the East; 1612, George Wither, Prince Henrie’s Obsequies, Elegy 24, in Egerton Brydges (editor), Restituta, Volume I, London: Longman, Hurst, Rees, Orme & Brown, 1814, p. 399, Though kept by Rome’s and Mahomet’s chiefe powers; They should not long detain him there in thrall
2. (obsolete, transitive) To make plain or manifest; to explain.

Etymology 4

From Middle English pleyn, borrowed from Old French plein, from Latin plēnus (“full, filled, complete”). Ultimately from Proto-Italic *plēnos, from Proto-Indo-European *pl̥h₁nós (“full”). Doublet of plene, plenary, and full.

adj

1. (obsolete) Full, complete in number or extent.