# What is difference between predicate logic, proportional logic and first order predicate logic?

1. Predicate Logic: Predicate logic is the general form of all logics that uses predicates, like q(x). Here q is predicate. Predicate logic supports the ability to have variables, and quantifiers. For example, xy.p(x,y) means "For all x there exists a y such that the proposition p(x,y) is true".
2. Propositional Logic: Propositional logic means without ability to do predication. For example, in P ^ Q, both p and q are propositions.
3. First order predicate logic:In first-order predicate logic, variables can appear only inside a predicate. That is, you can quantify over variables, but not predicates themselves. In second-order logic, you can also quantify over predicates, e.g. px.p(x)¬p(x) is true: for every predicate p, either p(x) or not p(x) is true, regardless of what x is.