Magma

A magma is a set closed to a binary operation.

When we say it is closed to that operation we mean that we could take any two elements of the set and put them through the operation and the result is something that is also in the set. Also, we can take the same element twice and produce something which is in the set.

Appendix A

You need to be aware of the conventions used by the author of any textbook you are using in a class like abstract algebra or modern algebra.

An expression like “a set S with a binary operation +” might indicate that S is closed to +.

We can create a set with elements that can be put through an operation but the set is not closed to that operation. However, I’ve never seen a set like that used in any math course – – yet.