1. [n]  a self-contained component (unit or item) that is used in combination with other components
2. [n]  computer circuit consisting of an assembly of electronic components (as of computer hardware)
3. [n]  detachable compartment of a spacecraft
4. [n]  one of the inherent cognitive or perceptual powers of the mind

1. \Mod"ule\, n. [F., fr. L. modulus a small measure, dim.
   of modus. See {Mode}, and cf. {Model}, {Modulus}, {Mold} a
   matrix.]
   1. A model or measure.
   2. (Arch.) The size of some one part, as the diameter of
      semi-diameter of the base of a shaft, taken as a unit of
      measure by which the proportions of the other parts of the
      composition are regulated. Generally, for columns, the
      semi-diameter is taken, and divided into a certain number
      of parts, called minutes (see {Minute}), though often the
      diameter is taken, and any dimension is said to be so many
      modules and minutes in height, breadth, or projection.
   

2. \Mod"ule\, v. t. [See {module}, n., {Modulate}.]
   To model; also, to modulate. [Obs.] --Sandys. Drayton.
   

1. An independent piece of software which forms part of one or more larger programs. Different languages have different concepts of a module but there are several common ideas.

Modules are usually compiled seperately (in compiled languages) and provide an abstraction or information hiding mechanism so that a module's implementation can be changed without requiring any change to other modules. In this respect they are similar to objects in an object-oriented language, though a module may contain many procedures and/or functions which would correspond to many objects.

A module often has its own name space for identifiers so the same identifier may be used to mean different things in different modules.

2. An independent assembly of electronic components with some distinct function, e.g. a RAM module consisting of several RAM chips mounted on a small circuit board.