In relational algebra, we have join and join-like operations.
I'm wondering if there is a formal name for the two operands on a join-like operation? For instance if we have two numbers, and wish to add them together, then the operation is addition, and its two operands are the augend and the addend.
Is there anything similar when the operation is join? What are the formal names for the two sets which act as operands/inputs to the join?