The word apparatus, when referring collectively to the tools and equipment for a particular activity or purpose, is noncount (uncountable). It is always singular.
We do not insert the indefinite article a or an before it.
- I am impressed by your city’s fire-fighting apparatus.
- We need to stock up on laboratory apparatus such as glassware, alcohol burners, ring stands, and safety gear.
When referring to the “structure of a system or an organization, particularly that of a political party or a government,” some dictionaries offer the countable apparatus—that is, we can use the indefinite article a or an with this word. Even so, the countable apparatus remains singular.
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