Feedback is usually defined something like this: "The control of input as a function of output by returning a portion of the output to the input"1 or "the transfer of energy from the output to the input of a system, or from one part of a system to another in a direction opposite to the main flow of energy."2 Computer scientists may wish to substitute the word "information" for that of "energy."

Since any input must propagate in a system before an output results, there seems to be a definite temporal nature to the concept of feedback. For this reason I would like to offer my own definition for consideration:

This definition also avoids the problem of tying the definition to "a portion of the output" or "the input." Freeing the definition from these constraints may make sense because a feedback "loop" may occur within the information flow boundaries of input and output.

1 McGraw-Hill dictionary of Physics and Mathematics, 1978, p. 353.

2 "Feedback," Van Nostrand's Scientific Encyclopedia, 1983, p. 1150.

3 Curtis D. Johnson, Process Control Instrumentation Technology (Englewood Cliffs, NJ: Prentice Hall, 1988), p. 3.

Homepage of David Lee Winston Miller.

Professional Resume