General:
* Diversion
* Interruption
* Interference
* Disturbance
* Disruption
* Dereliction
* Detachment
* Inattentiveness
More specific:
* For focus: Distraction can mean something that takes away from your concentration. Synonyms include:
* Disturbance
* Diversion
* Interference
* Distraction (the most direct synonym)
* For entertainment: Distraction can also refer to something that provides entertainment or amusement. Synonyms include:
* Diversion
* Entertainment
* Amusement
* For mental state: Distraction can also refer to a state of being preoccupied or not focused. Synonyms include:
* Inattentiveness
* Scatterbrainedness
* Absentmindedness
* Preoccupation
The best synonym to use will depend on the specific context and the nuance you want to convey.