monad

noun7

1. •
   One thing, one being, one item.
2. •
   A monoid object in the category of endofunctors of a fixed category.
3. •
   A data type which represents a specific form of computation, along with the operations "return" and "bind".

   • The properties that make the Maybe type a monad are its type constructor Maybe a, our chaining function (>>?), and the injector function Just. — 2008
4. •
   A single individual (such as a pollen grain) that is free from others, not united in a group.
5. •
   An ultimate atom, or simple, unextended point; something ultimate and indivisible.
6. •
   A group of entities or items treated as one entity.
7. •
   (old-fashioned) A single-celled organism. (See Monas.)