A unified approach is presented to analyzing various types of discrete and continuous time invariant/varying robust adaptive control systems.The approach provides a general guideline for the design of robust adaptive controllers.The essential tool of analysis is the inductive technique.Then we further develop the existing robust adaptive control theory.With the proposed unified approach, all the assumptions related to the a priori knowledge of modelling errors, which is required for the design and implementation of some existing robust adaptive controllers, can be removed.Also, the class of modelling errors including unmodelled dynamics and bounded external disturbances is enlarged in the sense that a looser bound can be allowed in the stability analysis.Some reviews on recent developments in adaptive control are provided, in which the issues including adaptive compensation for non-smooth nonlinearities and actuator failures, adaptive control of underactuated nonholonomic systems, distributed adaptive consensus control and stochastic adaptive control are discussed in detail.