energy, free energy -- ((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")
energy, vigor, vigour, zip -- (forceful exertion; "he plays tennis with great energy"; "he's full of zip")
energy, push, get-up-and-go -- (enterprising or ambitious drive; "Europeans often laugh at American energy")
energy, muscularity, vigor, vigour, vim -- (an imaginative lively style (especially style of writing); "his writing conveys great energy"; "a remarkable muscularity of style")
energy, vim, vitality -- (a healthy capacity for vigorous activity; "jogging works off my excess energy"; "he seemed full of vim and vigor")
energy -- (any source of usable power; "the DOE is responsible for maintaining the energy policy")