a monoid in an endofunctor category

A monad is a monoid in an endofunctor category.

a design pattern that allows structuring programs generically while automating away boilerplate code needed by the program logic

In functional programming, a monad is a design pattern that allows structuring programs generically while automating away boilerplate code needed by the program logic.

a design pattern concept used in mostly functional programming languages like lisp or in the modern world clojure or scala

A monad is a design pattern concept used in mostly functional programming languages like lisp or in the modern world clojure or scala.

that wraps another object

A monad is an object that wraps another object.

a structure that represents computations

In functional programming, a monad is a structure that represents computations.

a container type

*: 'A monad is a container type together with a few methods defined on a few methods .

a type of functor

In category theory, a monad is a type of functor.

an object that wraps another object in Scala that performs successive calculations such that the output of a calculation at any step is the input to other calculations, which run as a parent to the current step

A Monad is an object that wraps another object in Scala that performs successive calculations such that the output of a calculation at any step is the input to other calculations, which run as a parent to the current step.

a design pattern that is useful in purely functional languages such as Haskell

Somewhere, somebody is going to hate me for saying this, but if I were to try to explain monads to a Java programmer unfamiliar with functional programming, I would say: 'Monad is a design pattern that is useful in purely functional languages such as Haskell.

a design pattern invented to address a shortcoming in 'pure' functional languages

FP practitioners may not realize this, but a monad is a design pattern invented to address a shortcoming in 'pure' functional languages.

a design pattern that defines how functions, actions, inputs, and outputs can be used together to build generic types, with the following organization

In functional programming, a monad is a design pattern that defines how functions, actions, inputs, and outputs can be used together to build generic types, with the following organization.

a simple kind of error monad, where all errors are represented by Nothing

a monad is a simple kind of error monad, where all errors are represented by Nothing.

an abstract concept used in functional programming to sequence computation

A monad is an abstract concept used in functional programming to sequence computation, but computation can also be useful in OOP.

a pattern for doing function composition with ‘amplified’ types

I won’t go into the details of explaining monads, but in essence a monad is a pattern for doing function composition with ‘amplified’ types (as Mike Hadlow puts ‘amplified’ types very eloquently on Mike Hadlow's blog series about monads).

a data type that implements the Monad typeclass

A monad is a data type that implements the Monad typeclass.

a simple kind of error monad, where all errors are represented by None

a monad is a simple kind of error monad, where all errors are represented by None.

an object that encapsulates an operation

A Monad (besides the professorial definition you could find on the Internet) is an object that encapsulates an operation (in fact this definition is much more understandable for a programmer).

a mathematical abstraction of an operation that can conceptually have external effects

A monad is a mathematical abstraction of an operation that can conceptually have external effects.