groupoid

In abstract algebra, a groupoid, also called a magma, is an algebraic structure that has a single closed, binary operation defined on it and no other axioms. If the groupoid is represented M and its binary operator generically represented as •, then

for all a, b in M, a • b is also in M.

In mathematical notation, this is:

∀ a, b ∈ M: a • b ∈ M

This requirement is known as the magma axiom or closure axiom.