Prolog Error: Full stop in clause-body? Cannot redefine ,/2

Question

I just started learning prolog. I compiled a file with SWI-Prolog but got an error message: Prolog Error: Full stop in clause-body?

My file:

loves( vincent   , mia ) .
loves( marsellus , mia ) .

jealous(X,Y) :=
  loves(X,Z) ,
  loves(Y,Z) .

Answer 1

My mistake, I realized that it's should be :-, not :=.