solitary (adj.)

mid-14c., "alone, living alone," from Old French solitaire, from Latin solitarius "alone, lonely, isolated," from solitas "loneliness, solitude," from solus "alone" (see sole (adj.)). Meaning "single, sole, only" is from 1742. Related: Solitarily; solitariness. As a noun from late 14c.; from 1854 as short for solitary confinement (that phrase recorded from 1690s).

Definitions of solitary
solitary (adj.)
being the only one; single and isolated from others;
a solitary instance of cowardice
a solitary speck in the sky
Synonyms: lone / lonesome / only / sole
solitary (adj.)
characterized by or preferring solitude;
a man of a solitary disposition
a solitary walk
Synonyms: lone / lonely
solitary (adj.)
lacking companions or companionship;
a solitary traveler
Synonyms: alone / lone / lonely
solitary (adj.)
of plants and animals; not growing or living in groups or colonies;
solitary bees
Synonyms: nongregarious / nonsocial
solitary (adj.)
devoid of creatures;
a solitary retreat
Synonyms: lonely / unfrequented
solitary (n.)
confinement of a prisoner in isolation from other prisoners;
he was held in solitary
Synonyms: solitary confinement
solitary (n.)
one who lives in solitude;
Synonyms: hermit / recluse / solitudinarian / troglodyte