apparatus
Americannoun
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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.
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any complex instrument or mechanism for a particular purpose.
- Synonyms:
- contrivance, contraption, device, appliance, machine
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any system or systematic organization of activities, functions, processes, etc., directed toward a specific goal.
the apparatus of government; espionage apparatus.
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Physiology. a group of structurally different organs working together in the performance of a particular function.
the digestive apparatus.
noun
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a collection of instruments, machines, tools, parts, or other equipment used for a particular purpose
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a machine having a specific function
breathing apparatus
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the means by which something operates; organization
the apparatus of government
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anatomy any group of organs having a specific function
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.
Other Word Forms
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.
Vocabulary lists containing apparatus
Orbiting Jupiter
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Among the Hidden
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The Time Machine
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
The Cal Fire engine’s driver and two other firefighters riding in the apparatus were transported to Inland Valley Hospital for evaluation.
From Los Angeles Times • Jun. 6, 2026
Shadow home secretary Chris Philp said more than 73,000 migrants had crossed the Channel since Labour came to power and the apparatus to remove those with no right to stay was collapsing.
From BBC • Jun. 5, 2026
A former Democrat, Gabbard was a surprising choice to lead the giant US spy apparatus given her previous history of questioning intelligence and opposition to America's foreign military interventions.
From Barron's • May 22, 2026
More than a decade into his political ascent, it’s remarkable how thoroughly the lesson of Donald Trump has been internalized by the apparatus around him.
From Salon • May 18, 2026
But like violent crime in general, the murder rate cannot explain the growth of the penal apparatus.
From "The New Jim Crow" by Michelle Alexander
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
