Part, module, etc., Latin: componere - compound, put together, compose. Thus: A component is a part of a system whereas each component itself may consist of individual components and sub-components (elements, ingredients, modules, etc.) as well. If a material is termed one-, two- or multicomponent, depends on its state before the application.
One-component: One-component material is provided by the manufacturer ready for use (e.g. one-component adhesives, paints, etc.) or it must be prepared prior to application (e.g. dry mortar with water). One-component materials harden due to physical processes and/or chemical reactions, as e.g. the reaction with water/air humidity (concrete, mortar, PUR), evaporation (solvents), radiation (UV, IR).
Two-component: Two-component materials harden by reaction of the two components with each other so that they may be brought together only prior to application. Here too the (main) components are provided either ready for use or one component/both components must be prepared first.
Multicomponent: For multicomponent materials is valid as well that the (main) components are provided ready for use or single ones/all of them must be prepared first.
