Heavy is an adjective with different meanings:
Adjective:
1. Great weight
2. Great amount, quantity or size
3. Great force, intensity, turbulence
4. More than the usual or average weight
http://dictionary.reference.com/browse/heavy
Light is an adjective with different meanings:
Adjective:
1. Little weight; not heavy
2. Little weight in proportion to bulk
3. Less than the usual or average weight
4. Weighing less than the proper or standard amount
5. Small amount, force, intensity
