What’s the Plural of “Apparatus”?

The word “apparatus” can cause confusion because people are unsure if it is singular or plural or how to modify it for singular and plural nouns. This page explains in detail the plural form of “apparatus” and shows the term in example sentences.

What’s the Plural of “Apparatus”?

The plural form of the word “apparatus” is “apparatuses”, according to the Cambridge Dictionary. The term originally comes from Latin, which uses “apparatus” for both singular and plural; however, as English has adapted, the form “apparatuses” has become the standard plural version.

plural of apparatus

According to the Cambridge Dictionary, the word “apparatus” refers to a set of equipment, items, or tools used for a particular task.

Even though ”apparatus” is countable and has a plural form, in English, the word “apparatus” is commonly used as an uncountable noun to refer to both one or multiple “apparatus.” Therefore, it is common to see people use “apparatus” to refer to numerous pieces of equipment, or they may add something like “pieces of” when referring to several pieces of equipment.


The word “apparatus” comes from Latin and refers to items or equipment used for a particular task. Even though there is a plural form of “apparatus”, most people incorrectly assume it is an uncountable noun and use it the same way they would other uncountable nouns like “furniture.”

Therefore, instead of using the plural version, people often add something before it, such as “two pieces of” to refer to more than one piece of “apparatus.”

Here are some examples of the word “apparatus” in a sentence:

  • We couldn’t perform the experiment because we didn’t have the correct apparatus.
  • They use a particular type of apparatus that discreetly captures customer data.
  • The teacher let the students get familiar with each piece of apparatus before giving the instructions.
  • The brain is the apparatus with which we think and make decisions.


According to the Cambridge Dictionary, the word “apparatuses” is the plural form of the word “apparatus.”

“Apparatuses” is a plural form that has adapted over time since the English language started borrowing the word “apparatus” from Latin, for which “apparatus” is both singular and plural.

Despite the existence of the word “apparatuses”, many people are unaware of its existence and treat “apparatus” as an uncountable noun rather than a countable one.

Nevertheless, the plural form does exist and here are some examples of “apparatuses” in a sentence:

  • Many COVID patients used breathing apparatuses bought online to try and improve respiration.
  • You can have all the best apparatuses, but they are not much use if the staff don’t know how to operate them.
  • Apparatuses are available to help eradicate the problem of heavy snoring.


The word “apparati” does not exist and is not found in any major English dictionaries.

You may see the word from time to time, but it is an example of hypercorrection when people incorrectly assume a particular rule exists, leading to the belief transferring over into the actual language usage.

Another common word for which hypercorrection has resulted in an incorrect plural form is “octopus”, which in English should be “octopuses” rather than “octopi.” However, the word “octopi” has become so widespread that it is now regarded as a standard plural form.

Which Is Used the Most?

The Google Ngram shows that “apparatus” is used far more than “apparatuses” or “apparati.” The trend in the graph shows that most of the time, people use the word “apparatus” as an uncountable noun to refer to one piece of “apparatus” or multiple “pieces of apparatus.”

plural of apparatus usage

The second Google Ngram, comparing “apparatuses” and “apparati”, shows that the former is far more common and that the term “apparati” has barely appeared in literature in the last 100 years.

apparatuses vs apparati

Final Thoughts

The plural form of “apparatus” is “apparatuses”, according to the Cambridge Dictionary. However, many people treat the word “apparatus” as an uncountable noun and use something like “pieces of” before “apparatus” to specify a plural quantity.