n. 1. an instrument, piece of equipment, used in an experiment for various purposes, such as delivering stimuli or measuring responses during an experiment. 2. in biology, this also refers to a group or system of structures that perform a particular function when added to each other. It may be microscopic, as in the intracellular Golgi apparatus, or macroscopic, as in the vestibular apparatus.
APPARATUS: “The person needed a lot of apparatus for the experiment, including a Bunsen burner, a test tube, and some chemicals.”