olemus
ühikelemendiga poolrühm
= semigroup with unit element

ülevaateid
http://www.euclideanspace.com/maths/discrete/groups/monoid/index.htm

https://en.wikibooks.org/wiki/Haskell/Monoids

https://encyclopediaofmath.org/wiki/Monoid

https://blog.axosoft.com/monoids-practical-category-theory/

https://en.wikipedia.org/wiki/Monoid

https://en.wikipedia.org/wiki/Monoid_(category_theory)

rakendusi
http://dcapwell.github.io/scala-tour/Monads%20and%20Monoids.html

http://comonad.com/reader/wp-content/uploads/2009/08/IntroductionToMonoids.pdf