this is a traditional set from Set Theory
Monoid in Set Theory #card #bidirectional
defined as a set of elements
some operation for that set
can take in multiple elements from the set and return one from the set
has to be defined for all elements of the set
one element is the Unit element
Commutative and Associative
Examples
multiplication, Unit element = 1
string concatenation, Unit element = "" (empty string)
appending lists
Relates to Set Theory.