Final answer:
The term 'variable' describes something that can vary between experimental groups, and it is a crucial element to control and manipulate in experimental research.
Step-by-step explanation:
The term in question refers to a variable. In the context of experimental research, a variable is anything that can change or be changed, including things that vary in quantity (quantitative variables) or type (qualitative variables). Experiments aim to determine how independent variables influence dependent variables, and experimental groups are usually differentiated by changing one or more variables between them. A controlled variable is what remains unchanged across experimental groups, while the independent variable is what the experimenter changes to observe the effect on the dependent variable. It is vital to ensure that only the intended variables differ between groups to maintain the integrity of the experiment.