COMSOL Multiphysics is a finite element analysis, solver and Simulation software / FEA Software package for various physics and engineering applications, especially coupled phenomena, or multiphysics. The package is cross-platform (Windows, Mac, Linux). In addition to conventional physics-based user interfaces, COMSOL Multiphysics also allows for entering coupled systems of partial differential equations (PDEs). The PDEs can be entered directly or using the so-called weak form (see finite element method for a description of weak formulation). Since version 5.0 (2014), COMSOL Multiphysics is also used for creating physics-based apps. These apps can be run with a regular COMSOL Multiphysics license but also with a COMSOL Server license. An early version (before 2005) of COMSOL Multiphysics was called FEMLAB.