Capacity or power for work or vigorous activity
One's internal powers
Vigor in expression or action
Power developed or released by a device
The boy was no longer sleepy, but full of energy and excitement.
Now put that energy into walking.
Vastly more energy than we need pours down on this planet in the form of sunlight.
He already felt the loss of her calm energy, but he had no idea what to do about it.
She channeled her energy towards it, feeding it.