:: deftheorem defines Subspace-like RUSUB_4:def 7 :
for V being non empty RLSStruct
for S being non empty Subset of V holds
( S is Subspace-like iff ( 0. V in S & ( for x, y being Element of V
for a being Real st x in S & y in S holds
( x + y in S & a * x in S ) ) ) );