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

Class I. Words Expressing Abstract Relations
Section V. Number
2. Determinate Number

87. Unity.

   NOUN:UNITY; oneness &c. adj.; individuality; solitude (seclusion) [See Seclusion. Exclusion]; isolation (disjunction) [See Disjunction]; unification [See Combination]; completeness [See Completeness].
  ONE, unit, ace, monad; individual; none else, no other, nought beside.
  INTEGER, item, point, module.
   VERB:BE ONE, be alone &c. adj.
  ISOLATE (disjoin) [See Disjunction].
  RENDER ONE; unite (join) [See Junction], (combine) [See Combination].
   ADJECTIVE:ONE, sole, only-begotten, single, solitary, companionless; individual, apart, alone; kithless.
  UNACCOMPANIED, unattended; solus (fem., sola) [L.], single-handed; singular, odd, unique, unrepeated, azygous, first and last; isolated &c. (disjoined); insular.
  MONADIC, monadical; unific, uniflorous, unilobed, uniglobular, unifoliolate, unigenital, uniliteral, unilocular, unimodular, unitary; monospermous.
  insecable [obs.], inseverable, indiscerptible; compact, irresolvable.
  LONE, lonely, lonesome; desolate, dreary.
   ADVERB:SINGLE &c. adj.; alone, by itself, per se [L.], only [rare], apart, in the singular number, in the abstract; one by one, one at a time; simply; one and a half, sesqui-.
  1. Natura il fece, e poi roppe la stampa.
  2. Du fort au faible.
  3. Two souls with but a single thought, two hearts that beat as one.