energy in WordNet English dictionary

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