arbitrary vs plain

arbitrary

adj
  • Not representative or symbolic; not iconic. 

  • Determined by independent arbiter. 

  • Determined by impulse rather than reason; heavy-handed. 

  • Based on individual discretion or judgment; not based on any objective distinction, perhaps even made at random. 

  • Any, out of all that are possible. 

noun
  • Anything arbitrary, such as an arithmetical value or a fee. 

plain

adj
  • Ordinary; lacking adornment or ornamentation; unembellished. 

  • Downright; total, unmistakable (as intensifier). 

  • Clear; unencumbered; equal; fair. 

  • Not a trump. 

  • Containing no extended or nonprinting characters (especially in plain text). 

  • Not unusually beautiful; unattractive. 

  • Evident to one's senses or reason; manifest, clear, unmistakable. 

  • Honest and without deception; candid, open; blunt. 

  • Simple in habits or qualities; unsophisticated, not exceptional, ordinary. 

  • Having only few ingredients, or no additional ingredients or seasonings; not elaborate, without toppings or extras. 

  • Of just one colour; lacking a pattern. 

noun
  • A lamentation. 

  • An expanse of land with relatively low relief, usually exclusive of forests, deserts, and wastelands. 

adv
  • Simply. 

How often have the words arbitrary and plain occurred in a corpus of books? (source: Google Ngram Viewer )