落後 [ㄌㄨㄛˋ ㄏㄡˋ; luo4 hou4]
  to fall behind
  to lag (in technology etc)
  backward
  to retrogress
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  落伍
  落後
  らくご
  noun (common) (futsuumeishi)
  noun or participle which takes the aux. verb suru
  dropping out of
  straggling
  falling out of the ranks
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