noun
apparatus
ap-uh-RAT-us/ˌæpəˈrætəs/
An organized set of components serving a particular function.
The laboratory's apparatus separates the liquid into several different components.

Etymology
The pieces express making something ready. Latin used the resulting noun for preparation and equipment, giving English the idea of tools brought together for a particular purpose.
In context
"This is an apparatus called an ondometer. It tells you the direction and something of the magnitude of the Hertzian waves used in wireless."
More examples
- The exercise requires a complicated piece of apparatus.
- The party's political apparatus organized the entire campaign.
- The diagram shows the body's respiratory apparatus.
Forms
apparatus · apparatuses