apparatus

American  

[ap-uh-rat-uhs, -rey-tuhs] / ˌæp əˈræt əs, -ˈreɪ təs /

noun

plural

apparatus, apparatuses

1. a group or combination of instruments, machinery, tools, materials, etc., having a particular function or intended for a specific use.

   Our town has excellent fire-fighting apparatus.

2. any complex instrument or mechanism for a particular purpose.

   Synonyms:

   contrivance, contraption, device, appliance, machine

3. any system or systematic organization of activities, functions, processes, etc., directed toward a specific goal.

   the apparatus of government; espionage apparatus.

4. Physiology. a group of structurally different organs working together in the performance of a particular function.

   the digestive apparatus.

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apparatus British  

/ ˌæpəˈreɪtəs, ˈæpəˌreɪtəs, -ˈrɑːtəs /

noun

1. a collection of instruments, machines, tools, parts, or other equipment used for a particular purpose

2. a machine having a specific function

   breathing apparatus

3. the means by which something operates; organization

   the apparatus of government

4. anatomy any group of organs having a specific function

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Usage

Plural word for apparatus The plural form of apparatus can be either apparatus or apparatuses. The appropriate plural form depends on whether the term is considered to be a mass (uncountable) noun (like air or rice) or a count noun (like apple or car). When used as a mass noun, the correct plural form is apparatus, as in The lab apparatus must be removed before the lab can be painted. When used as a count noun, the correct plural form is apparatuses, as in The ship is equipped with apparatuses for security, cargo loading, and more. The plurals of several other singular words that end in -s are also formed the same way, such as pass/passes, lotus/lotuses, and dress/dresses. In some nouns that end in -us that are derived from Latin, the irregular plural ending -i may be used instead, as in fungus/fungi or cactus/cacti. These nouns are considered irregular nouns. However, this ending is not valid for apparatus. Apparati would be an invalid plural for apparatus.

Etymology

Origin of apparatus

1620–30; < Latin apparātus equipment, originally the act of equipping, preparation, equivalent to apparā ( re ) to prepare ( ap- ap- ¹ + parāre; see prepare) + -tus suffix of v. action

Explanation

Your apparatus is the collective equipment you use for specific purposes. For example, the apparatus used for scuba diving includes goggles, flippers, and a breathing tank, while a surgeon’s apparatus includes various scalpels and clamps. Different activities, different apparatuses. The noun apparatus evolved from the Latin apparātus, meaning "equipment or preparation." It might refer to one item, (a breathing apparatus) or a group of items (sports apparatus). Here’s a spelling tip: often, when a word ends in -us, the plural ending changes to i — “alumnus/alumni,” “focus/foci.” However, apparatus is part of the group that doesn't change — words like “virus/viruses” or “census/censuses.” This means the plural is either apparatus or apparatuses, though the latter is more common.

Example Sentences

There’s still plenty of eye rolling in China at caricatures of the U.S. presented by the propaganda apparatus.

From The Wall Street Journal • Apr. 19, 2026

Once Kansas City police have trained counterdrone personnel and installed detection equipment for soccer matches at Arrowhead Stadium, that capability does not disappear — it becomes part of the local security apparatus.

From MarketWatch • Apr. 13, 2026

When he shot into prominence in 2024, Magyar had no party apparatus behind him.

From Barron's • Apr. 3, 2026

Dyszel built frames for neutron tracking detectors and assembled them within the experimental apparatus.

From Science Daily • Mar. 13, 2026

That was especially true of the Rad Lab’s work with heavier elements, which required bombardments at energies well beyond the relatively meager powers of the Cavendish’s Cockcroft-Walton apparatus.

From "Big Science" by Michael Hiltzik

Related Words

• appliance
• device
• gear
• gizmo
• machine
• machinery
• means
• mechanism