Structural analysis deals with the determination of response of the structure subjected to loads. The rapid development of computers and the need for complex and light weight structures lead to the development of matrix methods of structural analysis. The classical methods of structural analysis, such as the method of consistent deformation, slope-deflection methods, consider the behavior of the entire structure for developing equations necessary for analysis. There exists two ways by which a structure is analyzed using matrix methods, namely the flexibility method or the force method and the stiffness method or the displacement method. This chapter discusses the important terms and their definitions used in matrix methods of analysis. Depending on the method of analysis, there are two types of indeterminacy, namely degree of kinematic indeterminacy (DKI) and degree of static indeterminacy (DSI). The degrees of freedom (DOF) of a node are the number of independent displacements that the node can undergo.