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What Part of Speech Is “Is”?

Updated on October 11, 2023Grammar

Is is one of those words you might not think about much. After all, it’s such a short word, and it’s in so many of the sentences you say and write. Because it’s so common, it can be easy to overlook.

But what is is really?

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What part of speech is is?

Is is a verb. It’s the third-person singular form of to be. Take a look at the forms to be takes depending on its tense and number:

Subject To be form
I (first-person singular) am
You (second-person singular) are
She/he/it (third-person singular) is
We (first-person plural) are
You (second-person plural) are
They (third-person plural) are


Every sentence contains at least one verb. Similarly, every sentence must have at least one noun. The process of these and other parts of speech working together is known as grammar.

In a sentence, is refers to the action of being. That’s a little different from how we normally think of verbs, which are usually described as “action words.” Is is a linking verb, which is a verb that describes the relationship between the subject of a sentence and a noun or an adjective in the same sentence. Here are a few examples:

  • She is my sister.
  • The flower is purple.

Is can also function as an auxiliary verb. Auxiliary verbs are verbs that support sentences’ main verbs. Here are a few examples of is in this role:

  • He is studying music theory.
  • Our grandmother is hosting the party.

What part of speech is to be?

As we mentioned above, is is a verb. Specifically, it can function as a linking verb or as an auxiliary verb. When a sentence contains an auxiliary verb, it must contain another verb as well. This other verb is the sentence’s main verb, and it describes the action that’s happening in the sentence. Take a look at these examples of is operating as an auxiliary verb:

  • It is snowing.
  • My literature class is challenging me.

Auxiliary verbs express a sentence’s tense, mood, or voice. For example, if we wanted to express that the literature class in our most recent example happened in the past, we would swap out is for was:

  • My literature class was challenging me.

Is is a form of another auxiliary verb: be. Every form of be, including was, been, are, and am, can function as auxiliary verbs. Other auxiliary verbs include:

  • have
  • has
  • had
  • do
  • could
  • should
  • would
  • does
  • may
  • might

Some of these verbs, such as might and could, fit into a subclass of auxiliary verbs called modal verbs. These verbs communicate intent, possibility, and necessity. Like other auxiliary verbs, modal verbs work with their sentences’ main verbs.

Is examples

As a linking verb

  • My niece is her class’s valedictorian.
  • Our library book is overdue.
  • The bear is brown.
  • Language Arts is my favorite class.

As an auxiliary verb

  • It is supposed to rain tonight.
  • My mother is training for a 5k.
  • As I recall the story, he is remembering the details.
  • My PC is running a new Linux distro.


What is the meaning of is?

Is is the third person singular form of the verb “be.”

What part of speech is the word is?

Is is a verb. As such, it describes the action of being.

How is is used in a sentence?

Is can be a linking verb or an auxiliary verb. When it functions as a linking verb, it links the sentence’s subject to another noun or an adjective. When it functions as an auxiliary verb, it supports the main verb in the sentence.

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