Is Prolog considered a functional programming language?

Prolog is not considered a functional programming language because it is primarily based on predicate logic and is classified as a logic programming language. In functional programming, the focus is on the evaluation of functions and the use of immutable data. Functional languages emphasize the use of mathematical functions and often employ higher-order functions and recursion as fundamental elements of their design.

In contrast, Prolog operates using a set of facts and rules to derive conclusions and make inferences. Its execution model is based on unification and backtracking rather than function evaluation. Prolog programs consist of logical assertions and rules, and computation in Prolog is achieved through querying these predicates rather than through function calls, which is the hallmark of functional programming.

This clear distinction in the design and operational paradigms between Prolog and functional programming languages solidifies the answer that Prolog is not a functional programming language.