composed of standardized units or sections for easy construction or flexible arrangement: a modular home; a modular sofa.

Mathematics. (of a lattice) having the property that for any two elements with one less than the other, the union of the smaller element with the intersection of the larger element and any third element of the lattice is equal to the intersection of the larger element with the union of the smaller element and the third element.

Computers. composed of software or hardware modules that can be altered or replaced without affecting the remainder of the system.

noun

something, as a house or piece of furniture, built or organized in self-contained units or sections.

a self-contained unit or item, as of furniture, that can be combined or interchanged with others like it to create different shapes or designs.

Origin of modular

From the New Latin word modulāris, dating back to 1790–1800. See module, -ar^{1}

1798, as a term in mathematics, from French modulaire or directly from Modern Latin modularis, from Latin modulus "a small measure" (see module). Meaning "composed of interchangeable units" first recorded 1936.