noun (n)

• (physics) a thermodynamic quantity equivalent to the capacity of a physical system to do work; the units of energy are joules or ergs(noun.phenomenon)

  Example:
  Energy can take a wide variety of forms.
  

  Synonym:
  free energy
  

  source: wordnet30
• forceful exertion(noun.attribute)

  Example:
  He plays tennis with great energy.
  

  Synonym:
  vigor, vigour, zip
  

  source: wordnet30
• enterprising or ambitious drive(noun.attribute)

  Example:
  Europeans often laugh at American energy.
  

  Synonym:
  get-up-and-go, push
  

  source: wordnet30
• an imaginative lively style (especially style of writing)(noun.attribute)

  Example:
  His writing conveys great energy.
  

  Synonym:
  muscularity, vigor, vigour, vim
  

  source: wordnet30
• a healthy capacity for vigorous activity(noun.state)

  Example:
  Jogging works off my excess energy.
  

  Synonym:
  vim, vitality
  

  source: wordnet30
• any source of usable power(noun.phenomenon)

  Example:
  The DOE is responsible for maintaining the energy policy.
  

  source: wordnet30
• the federal department responsible for maintaining a national energy policy of the United States; created in 1977(noun.group)

  Synonym:
  department of energy, doe, energy department
  

  source: wordnet30
• Internal or inherent power; capacity of acting, operating, or producing an effect, whether exerted or not; as, men possessing energies may suffer them to lie inactive.(noun)

  source: webster1913