Modularity is an attribute of a system that can be decomposed into a set of cohesive entities that are loosely coupled. Many cellular networks can be decomposed into functional modules—each functionally separable from the other modules.
E.g A functional module is defined as a group of genes or their products which are related by one or more genetic or cellular interactions, e.g. co-regulation, co-expression or membership of a protein complex, of a metabolic or signaling pathway or of a cellular aggregate (e.g. chaperone, ribosome, protein transport facilitator, etc.). An important property of a module is that its function is separable from other modules and that its members have more relations among themselves than with members of other modules, which is reflected in the network topology.
