資料來源 : Free On-Line Dictionary of Computing

name capture
     
         In {beta reduction}, when a term containing a
        {free} occurrence of a variable v is substituted into another
        term where v is bound the free v becomes spuriously bound or
        "captured".  E.g.
     
        	(\ x . \ y . x y) y  -->  \ y . y y	(WRONG)
     
        This problem arises because two distinct variables have the
        same name.  The most common solution is to rename the bound
        variable using {alpha conversion}:
     
        	(\ x . \ y' . x y') y --> \ y' . y y'
     
        Another solution is to use {de Bruijn notation}.
     
        Note that the argument expression, y, contained a {free
        variable}.  The whole expression above must therefore be
        notionally contained within the body of some {lambda
        abstraction} which binds y.  If we never reduce inside the
        body of a lambda abstraction (as in reduction to {weak head
        normal form}) then name capture cannot occur.
     
        (1995-03-14)