Merriam-Webster Collegiate Dictionary - wane

 I. intransitive verb  (~d; waning)  Etymology: Middle English, from Old English wanian; akin to Old High German wanon to ~, Old English wan wanting, deficient, Latin vanus empty, vain  Date: before 12th century  1. to decrease in size, extent, or degree ; dwindle: as  a. to diminish in phase or intensity — used chiefly of the moon, other satellites, and inferior planets  b. to become less brilliant or powerful ; dim  c. to flow out ; ebb  2. to fall gradually from power, prosperity, or influence  Synonyms: see abate  II. noun  Date: 14th century  1.  a. the act or process of waning strength on the ~  b. a period or time of waning; specifically the period from the full moon to the new moon  2. Middle English, defect, from Old English wana; akin to Old English wan deficient a defect in lumber characterized by bark or a lack of wood at a corner or edge