Refers to the length of time something lasts or continues; used in technical and everyday contexts.
The duration of this medicine is about 8 hours.
The battery's span has become shorter.
期間 is a general term for a period or interval, while 持続時間 specifically emphasizes the continuous duration of a state or effect.
継続時間 is a near-synonym also meaning duration, but 持続時間 is more common in technical contexts like medicine or electronics.
Compound of 持続 (continuation) and 時間 (time).