adverb在(或向)…后面;落后于,积压(工作);在原来的地方
preposition在(或向)…后面;落后于;支持
adverbat or to the back of somebody or something
adverbslower or less good than you should be
adverbin the place where somebody or something was before
prepositionat or to the back of somebody or something
prepositionslower or less good than somebody or something
prepositiongiving support to somebody or something