Definition of Apparatus the tools, equipment, and machinery you use for particular purposes Examples of Apparatus in a sentence The firefighter donned a breathing apparatus before entering the blaze, to search for people trapped in the inferno. The president’s security apparatus fanned out so that they could keep watch on all angles of the event.

"apparatus" is a correct and usable word in written English. It is mainly used as a noun and refers to a set of equipment, or machines that are used for a specific purpose. Example sentence: The laboratory was filled with different types of scientific apparatus.

[uncountable] the tools or other pieces of equipment that are needed for a particular activity or task a piece of laboratory apparatus Firefighters needed breathing apparatus to enter the burning house. Science departments say they are lacking basic apparatus.