space

When we think of "space," we often think of "outer space" -- the vast, empty, dark space that surrounds the stars and planets. Just as space surrounds everything in the Universe, it surrounds you and everything around you. Space is the structure and fabric of the cosmos. Without space, physical phenomena could not occur.

What it is: the ability to do work
Main kinds of energy: potential and kinetic
Main units of measurement: joules or calories
Different forms: atomic, chemical, electric, mechanical, sound, heat, and light
Characteristics: changes from one form to another; can never be destroyed

Image credits: Eric Hamilton.