Plural of Apparatus
“Apparatus” can be uncountable when it means equipment as a mass and countable when it means a particular device, system, or organization. For countable plural use, “apparatuses” is standard; Cambridge American treatment also records invariant plural “apparatus.”
The main countable plural is “apparatuses.” Cambridge American material also records unchanged “apparatus” as a plural variant, while equipment use can be uncountable.
Key details
Choose the right form
| Meaning / situation | Form / construction | Decision |
|---|---|---|
| equipment as a mass | apparatus | Uncountable use. |
| several countable units/systems | apparatuses | Main plural. |
| several countable units/systems | apparatus | Recorded American plural variant. |
Quick tests
Plural-choice test
Are you counting separate devices, systems, or organizations?
If yes: Use “apparatuses”; invariant “apparatus” is also recorded in Cambridge American treatment.
If no: Use uncountable “apparatus” if you mean equipment as a mass.
Caveat: The source distinguishes countability and regional dictionary treatment; preserve that boundary.
Examples
The lab installed two new apparatuses.
“Apparatuses” is the main countable plural.
The divers checked their breathing apparatus.
Equipment use can be uncountable.
The American entry also permits several apparatus.
Invariant plural is a recorded variant, not the sole form.
Further guidance
Core difference
Use “apparatuses” for multiple countable apparatuses; unchanged plural “apparatus” is also recorded in Cambridge American treatment.
Fast Test
First decide whether “apparatus” is mass equipment or a countable unit/system.
Usage Boundary
Do not add a plural mechanically in mass-equipment use, and do not claim invariant plural “apparatus” is the only plural.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- APPARATUS | English meaning - Cambridge Dictionary (opens in a new tab)Cambridge University Press · Cambridge gives apparatuses as the main plural and its American dictionary treatment also records invariant apparatus, while equipment use can be uncountable.