IPA: /dɪˈteɪnmənt/
KK: /dɪˈteɪnmənt/
The state of being held in custody or confinement, often by authorities.
The suspect was held in detainment while the investigation continued.
Detainment is formed from "de-" (meaning down or away) and "tenere" (meaning to hold). The word refers to the act of holding someone down or away from freedom, typically in a legal context.
Think of 'holding down' ('tenere') someone 'away' ('de-') from their freedom — that's what detainment means.