I recently studying Gallian Abstract Algebra 8th edition by Pearson Book. And found an exercise of chapter "group" that asks to find binary operations which are closed.
But by the definition of binary operations $*:G\times G \to G $ is essentially closed because the definition says "Let G be a set.A binary operation on G is a function that assigns each ordered pair of elements of G an element of G". If the question be "which of following operations are closed ?", that is a better question. Am I right about the definition or I interpret in wrongly?