- predicate::glossary=An formula P(X,Y,Z,..) which can be true or false depending on the values assigned to the variables in it. Prolog can either attempt to find values for the variables to make the predicate true or it can test to see if the current assigned values make it true.
- operator::glossary=A prefix, postfix or infix symbol used in structures, expressions, and clauses.
- clause::glossary=A pair of statements, head and tail, joined together and stored in the Prolog data base. Normally a clause indicates that the head is true if the tail is true, but not vice versa.