"Interest in the project waned"
"Interest in his novels waned"
"the moon is waning"
She, like a moon in wane, Faded before him.
That which grows is said to wax, and that which decays to wane.
牛津高阶第八版
美国韦氏词典
Dictionary.com
Free Dictionary
维基百科 (自由的百科全书)