Found:

residue

SYNTAX: In checking theory, the residue of A is the domain of A minus its complement domain. EXAMPLE: In (i), the residue of X is ZP, UP, WP, H and whatever these categories dominate.

(i)    XP1
       /\
      /  \
     UP  XP2
        /\
       /  \
     ZP1    X'
    /\      /\
   /  \    /  \
  WP  ZP2  X1  YP
          /\
         /  \
        H   X2