•If A is a structure over vocabulary s
and a1, …, am 2 A
then (A,a1, …, am) denotes the structure over vocabulary sn = s [ {c1, …, cm} s.t. the interpretation
of each ci is ai
•
•In particular, (A,a) ' (B,b) means that there is an isomorphism A ' B
that maps a to b