Definitions of energy:

• noun:   an imaginative lively style (especially style of writing)

  Example: "His writing conveys great energy"

• noun:   enterprising or ambitious drive

  Example: "Europeans often laugh at American energy"

• noun:   an exertion of force

  Example: "He plays tennis with great energy"

• noun:   (physics) the capacity of a physical system to do work; the units of energy are joules or ergs

  Example: "Energy can take a wide variety of forms"

• noun:   a healthy capacity for vigorous activity

  Example: "Jogging works off my excess energy"

• noun:   the federal department responsible for maintaining a national energy policy of the United States; created in 1977