In general, a thing's components are its parts; the things that compose it.

• In telecommunication and computing, a component is an assembly, or part thereof, that is essential to the operation of some larger assembly and is an immediate subdivision of the assembly to which it belongs. For example, a radio receiver may be a component of a complete radio set consisting of a combined transmitter-receiver, i.e., a transceiver. The same radio receiver could also be a subsystem of the combined transmitter-receiver, in which case the IF amplifier section would be a component of the receiver but not of the radio set. Similarly, within the IF amplifier section, items, such as resistors, capacitors, vacuum tubes, and transistors, are components of that section.
• In logistics, a component is a part, or combination of parts having a specified function, that can only be installed or replaced as an entity.
• In manufacturing, a component is an assembly or any combination of parts, subassemblies, and assemblies mounted together in manufacture, assembly, maintenance, or rebuilding.
• For components in mathematics, see Connected component (graph theory) (for graphs) or Connected space (for general spaces).
• In physics, a component of a vector is its projection onto one of the axes of a coordinate system; for example only the horizontal and vertical components of the movement of a body.
• Somewhat more generally, in mathematics, the components of a tuple are the scalars that are its entries.
• In software, the word component has an emerging meaning generalizing the idea of a software pattern, software object, software framework and software architecture. software componentry can be any of these. See also: component software theory, software component.
• In thermodynamics, a component is a chemically distinct constituent of a phase of a system.
• In television and video, components are discrete channels for red, green, blue, sync, and sometimes other parts of the video signal (opposite of multiplex or composite video, which has subcarriers for colour). See audio and video connector.