:: deftheorem SUB defines -sub MSAFREE5:def 28 :
for S being non empty non void ManySortedSign
for X being non-empty ManySortedSet of the carrier of S
for s being SortSymbol of S
for x being Element of X . s
for C being context of x
for t being Element of (Free (S,X)) st the_sort_of t = s holds
C -sub t = (C,[x,s]) <- t;