Control refers to a specific technique that involves making measured and deliberate comparisons of the actual resultant performance with what was expected to be the planned performance. Control also refers to a systematic method of analyzing the variances that develop as a process unfolds. Control can also refer to the technique of assessing the trends that may develop during a specific activity or task or that begin to unfold during the broader time frame of the entirety or a project, as well as a thorough evaluation of all possible alternatives and a determination as to what corrective action should be taken to help turn a project back into a direction that is more conducive to the attainment of whatever ultimate goals and results are expected and/or anticipated. Control can also refer to a fixed point during the course of variant activities, such as utilization of the same type of machines to develop different types of products.
This term is defined in the 3rd and the 4th edition of the PMBOK.