Mawson, C.O.S., ed. (1870–1938). Roget’s International Thesaurus. 1922.

Class IV. Words Relating to the Intellectual Faculties
Division (II) Communication of Ideas
Section III. Means of Communicating Ideas
Various Qualities of Style

576. Plainness.

   NOUN:PLAINNESS &c. adj.; simplicity, simplex munditiis [Hor.], lack of ornamentation, severity; plain -terms, – English; Saxon English; household words.
   VERB:SPEAK PLAINLY, waste no words, call a spade a spade; plunge in medias res [L.]; come to the point.
   ADJECTIVE:PLAIN, simple; unornamented, unadorned, unvarnished; homely, homespun; neat; severe, chaste, pure, Saxon; commonplace, matter-of-fact, natural, prosaic, sober, unimaginative.
  DRY, unvaried, monotonous [See Feebleness].
   ADVERB:POINT-BLANK; in plain -terms, – words, – English; in common parlance.