:: deftheorem Def21 defines (SUBNETS) YELLOW_6:def 21 :
for T being non empty 1-sorted
for C being Convergence-Class of T holds
( C is (SUBNETS) iff for N being net of T
for Y being subnet of N st Y in NetUniv T holds
for p being Element of T st [N,p] in C holds
[Y,p] in C );