Cellmate (noun)

A person with whom one shares a cell, typically in a prison or other place of confinement.

Origin:

The word cellmate is composed of two words "cell" meaning a small room used for confinement and "mate" meaning a companion, referring to a person who shares a cell with another person.

Examples:

1. He was assigned a new cellmate after his previous one was transferred.
2. He had to adjust to life with a cellmate.
3. His cellmate was serving a life sentence.
4. The cellmate was a model prisoner.
5. He was worried about getting along with his new cellmate.