You wag or waggle something when you wave it backwards and forwards fairly fast. dogs wag their tails when they are happy. People sometimes wag their fingers to tell someone else off.
Video: view
Video: view
Something is waning when it is decreasing in size, intensity, strength or power. For example, "his health was waning".
The picture is of the waning moon. The opposite of waning is waxing.
You waste something when you have it, but you don't use it, or you use it for less important things. Someone might waste their money by buying lots of pairs of shoes and then complaining later they have no money for other things.
Waste is also leftovers, or something that is no longer needed and becomes trash. Anything you throw away is waste.