Linked from
The 15 pages that link to Binary operation, each with the reason it gives.
Group homomorphismNarrower topic: The operation is the structure a group homomorphism must preserve.
AssociativityNarrower topic: Associativity is a condition imposed on binary operations.
MonoidNarrower topic: It is the operation whose associativity and identity determine a monoid.
Inverse elementNarrower topic: An inverse is defined relative to a particular binary operation.