wane

Short definition from Wiktionary

Noun

1. 1
   A gradual diminution in power, value, intensity etc.
2. 2
   The lunar phase during which the sun seems to illuminate less of the moon as its sunlit area becomes progressively smaller as visible from Earth.
3. 3
   The end of a period.
4. 4
   A rounded corner caused by lack of wood, often showing bark.
5. 5
   A child.
6. 6
   A house or dwelling.

Verb

1. 1
   To progressively lose its splendor, value, ardor, power, intensity etc.; to decline.
2. 2
   For light to dim or diminish in strength.
3. 3
   For the Moon to pass through the phases of its monthly cycle where its surface is less and less visible.
4. 4
   Said of a time period that comes to an end.
5. 5
   To decrease physically in size, amount, numbers or surface.
6. 6
   To cause to decrease.