:: deftheorem Def2 defines Chi TOPGEN_2:def 2 :
for T being non empty TopStruct
for b₂ being cardinal number holds
( b₂ = Chi T iff ( ( for x being Point of T holds Chi (x,T) c= b₂ ) & ( for M being cardinal number st ( for x being Point of T holds Chi (x,T) c= M ) holds
b₂ c= M ) ) );