noun (n)

• a state of being confined (usually for a short time)(noun.state)

  Example:
  His detention was politically motivated.
  

  Synonym:
  custody, detainment, hold
  

  source: wordnet30
• a punishment in which a student must stay at school after others have gone home(noun.act)

  Example:
  The detention of tardy pupils.
  

  source: wordnet30
• The act of detaining or keeping back; a withholding.(noun)

  source: webster1913