Definition of "Energy" :

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

"His writing conveys great energy."

noun: enterprising or ambitious drive

"Europeans often laugh at American energy."

noun: forceful exertion

"He plays tennis with great energy."

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

noun: any source of usable power

"The DOE is responsible for maintaining the energy policy."

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

"Energy can take a wide variety of forms."

noun: a healthy capacity for vigorous activity

"Jogging works off my excess energy."