In scientific testing, a variable that is kept constant so that the impact of another factor can be better understood. This can be confusing because this use of the term is slightly different from wha [..]

A variable that must remain the same in all situations. Controlled variables are all of the things in an experiment that must remain the same.

In a Control loop (closed-loop control circuit), the controlled variable x is a variable changing over time that is to be brought to and kept at a specific value. A measuring device is used to feed ba [..]

a variable used to express the part of the exit condition of a loop that varies each time around the loop. For example ``i'' in for (int i=0; i<max; ++i) f(i);