modules

a separable component, frequently one that is interchangeable with others, for assembly into units of differing size, complexity, or function.

any of the individual, self-contained segments of a spacecraft, designed to perform a particular task: the spacecraft's command module; a lunar module.

a standard or unit for measuring.

a selected unit of measure, ranging in size from a few inches to several feet, used as a basis for the planning and standardization of building materials.

Mathematics. an Abelian group with a set of left or right operators forming a ring such that for any two operators and any group element the result of having the first operator act on the element, giving a second element, and the second operator act on the second element is equal to the result of having a single operator, formed by adding or multiplying the two operators, act on the first element. Compare ring¹ (def. 23).