Definition from Wiktionary, the free dictionary
interrogation (plural interrogations)
- The act of interrogating or questioning; examination by questions; inquiry.
- A question put; an inquiry.
- A point, mark, or sign, thus ?, indicating that the sentence with which it is connected is a question. It is used to express doubt, or to mark a query. Called also interrogation point.
Usage notes 
- Preposition under is generally used for the person or matter that is being investigated; Johnny is under interrogation about the last night's events.
Related terms 
act of interrogating or questioning
question put; an inquiry
interrogation f (plural interrogations)