A program result is the difference between the status of some condition prior to program implementation and the status of that condition after program implementation. There are several types of results. I am using terminology that is common in evaluation literature.
I am doing this exercise because I believe good evaluation involves using language precisely as different viewpoints are explored. For example, saying that a program achieves results is not precise use of language. Achievement is something that is a consequence of human action. So program implementation, the actions of human actors, achieves results.
Program effects are results directly related to expectations for the program, often in the form of aims, goals, and objectives.
Program impact are effects that are practically significant and sustained over a relatively long period of time. The evaluation needs to rule out plausible non-program factors that could have led to each effect; the evaluation reporting should include the conclusions of these efforts.
Side effects are results that are not directly related to program expectations.
Undesirable consequences are results that are harmful in someway.
I welcome comments.