Algebraic approaches mainly come from theoretical computer science. They have in common the assumption of a finite or recursive enumerable number of objects. Each object is considered as the smallest unit that can be handled by the system model. Both biomolecules and processes can form objects depending on the type of the algebraic approach. Interactions between objects or additional parameters about objects are specified by sets (relations) of acceptable system configurations. The whole description is based on discrete transitions. This allowes structural and comparative analysis of system composition and behaviour independent of numeric simulation results. In terms of their computational properties, term rewriting systems, state based systems, and process calculi can be distinguished.