| context | $M$ … set |
| definiendum | $ \langle\!\langle M,* \rangle\!\rangle \in$ magma |
| inclusion | $* \in$ binary operation (M) |
The binary operation is often called multiplication.
The axiom '$* \in$ binary operation (M)' above means that a magma is closed with respect to the multiplication.
One generally calls $M$ the Magma, i.e. the set where the operation “$*$” is defined on.
Wikipedia: Magma