Example : He was held in solitary.

Synonyms : solitary confinement

Synonyms : hermit, recluse, solitudinarian, troglodyte

Example : A lone wolf.
A lonely existence.
A man of a solitary disposition.
A solitary walk.

Synonyms : lone, lonely

Example : Solitary bees.

Synonyms : nongregarious, nonsocial

Example : He was alone when we met him.
She is alone much of the time.
The lone skier on the mountain.
A lonely fisherman stood on a tuft of gravel.
A lonely soul.
A solitary traveler.

Synonyms : alone, lone, lonely

Example : The lone doctor in the entire county.
A lonesome pine.
An only child.
The sole heir.
The sole example.
A solitary instance of cowardice.
A solitary speck in the sky.

Synonyms : lone, lonesome, only, sole

Example : A lonely crossroads.
A solitary retreat.
A trail leading to an unfrequented lake.

Synonyms : lonely, unfrequented