Solitude is a state of seclusion

Seclusion

The act of secluding, i.e. shutting out or keeping apart from society, or the state of being secluded, or a place that facilitates it . A person, a couple, or a larger group may go to a secluded place for privacy, or because the place is quiet...

 or isolation, i.e., lack of contact with people. It may stem from bad relationships, deliberate choice, infectious disease

Infectious disease

Infectious diseases, also known as communicable diseases, contagious diseases or transmissible diseases comprise clinically evident illness resulting from the infection, presence and growth of pathogenic biological agents in an individual host organism...

, mental disorders, neurological disorder

Circadian rhythm sleep disorder

Circadian rhythm sleep disorders are a family of sleep disorders affecting, among other things, the timing of sleep. People with circadian rhythm sleep disorders are unable to sleep and wake at the times required for normal work, school, and social needs. They are generally able to get enough sleep...

s or circumstances of employment or situation (see castaway

Castaway

A castaway is a person who is cast adrift or ashore. While the situation usually happens after a shipwreck, some people voluntarily stay behind on a deserted island, either to evade their captors or the world in general. Alternatively, a person or item can be cast away, meaning rejected or discarded...

).

Short-term solitude is often valued as a time when one may work, think or rest without being disturbed. It may be desired for the sake of privacy

Privacy

Privacy is the ability of an individual or group to seclude themselves or information about themselves and thereby reveal themselves selectively...

.

A distinction can be made between physical and mental seclusion.