What is the term used for being under arrest by a peace officer?

The term used for being under arrest by a peace officer is "custody." When an individual is taken into custody, it implies that law enforcement has the legal authority to restrict their freedom, usually due to suspected involvement in a crime. This state indicates that the person is formally detained for investigative or legal processes and is within the control of law enforcement.

Detention often applies to a temporary and less formal restraint, usually for questioning or investigative purposes, without the same legal implications. Imprisonment generally refers to being confined in a prison after a conviction, which is a separate stage in the legal process. Confinement also suggests physical restraining but lacks the specific legal connotation associated with law enforcement actions like custody. Therefore, "custody" accurately captures the circumstance of being under arrest by a peace officer.