Directly below; how important something is.
Undervalue
How heavy something is; make the word an adjective.
Weighty
How heavy something is; without; state of being.
Weightlessness
Directly below
Under
Directly below; how heavy something is.
Underweight
Directly below a group of people
Underclassmen
How heavy something is
Weight
How heavy something is; without
Weightless
Directly below; to put something on top.
Undercover
Directly below; make something visible.
Underexpose