wane          
 verb [ I ] uk/weɪn/ us/weɪn/
 衰减;减弱
to become weaker in strength or influence
  By the late 70s the band's popularity was beginning to wane. 上世纪70年代末,这支乐队的人气开始下滑。 
 Synonyms: decline (GO DOWN)decrease diminishdrop (LOWER)ebb (FEELING)
  formal(月亮)开始形成残月,亏缺 
The moon wanes when it gradually appears less and less round, after the full moon.
 Opposite: wax (MOON) 
 wane      
noun uk/weɪn/ us/weɪn/
on the wane (权力、人气等)衰落,减弱
becoming less strong, powerful, popular, etc.
  There are signs that support for the group is on the wane. 有迹象表明该组织的支持率正日益下降。 
 Synonym: ebb