:: deftheorem Def3 defines ExCl GOEDELCP:def 3 :
for Al being QC-alphabet
for b₂ being Subset of (CQC-WFF Al) holds
( b₂ = ExCl Al iff for a being set holds
( a in b₂ iff ex x being bound_QC-variable of Al ex p being Element of CQC-WFF Al st a = Ex (x,p) ) );