Experiments in which all variables are identical except for one are called experiments

Controlled experiments

Explanation:

Controlled experiments are those experiments where all variables are identical but only one is different. The purpose of such experiments is to test a hypothesis by analyzing the change it brings to results due to change of only one variable when everything else is constant. SO we can say that in such experiments, it is the only changing variable which is influencing the results of an experiment because everything else is just same.

Hope it helps!

that is wrong, its not thymus.