You’ve probably been using the word "can" since before you could tie your own shoes. It’s one of the first words we learn because it represents possibility, permission, and power. But if you’re sitting there wondering what parts of speech is can, you’ve stumbled into a surprisingly deep linguistic rabbit hole. Most people just shrug and say, "It’s a verb."
They aren't wrong. However, they aren't entirely right either.
Depending on whether you’re talking about your ability to run a marathon or that dusty tin of beans in the back of your pantry, "can" shifts its grammatical weight like a chameleon. It’s a helper. It’s an action. It’s an object. Honestly, it’s one of the most hardworking words in the English language, and understanding its specific roles can actually make you a much sharper writer.
The Modal Verb: Your Daily Workhorse
Most of the time, when you ask what parts of speech is can, you’re looking at a modal auxiliary verb. This is a fancy way of saying it’s a "helping" verb that doesn't stand alone very well.
Think about it. If you walk up to someone and just say, "I can," they’re going to wait for the rest of the sentence. You can what? Run? Sing? Eat a whole pizza? The modal verb "can" needs a main verb to give it purpose. It modifies the meaning of that main verb to express ability, permission, or even a theoretical possibility.
- "I can juggle." (Ability)
- "Can I go to the party?" (Permission—though your English teacher might insist on "may")
- "It can get cold in October." (Possibility)
Grammarians like Steven Pinker have often pointed out how these modal verbs function differently than "normal" verbs. For one, they don't change form. You’d never say "he cans juggle." It stays "can" regardless of the subject. It also doesn't have an infinitive form; you can't "to can" in the sense of being able to do something. This lack of flexibility is actually what makes it a "defective verb" in technical linguistic circles.
When It Becomes a Noun
But wait. What about that soda sitting on your desk?
In that context, "can" isn't a verb at all. It’s a noun. Specifically, it’s a countable noun referring to a cylindrical metal container. This is where the word's history gets interesting. The noun form actually predates a lot of modern usage, coming from the Old English canne, which referred to a cup or container.
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When you say, "Pass me that can of soup," you’re using a common noun. It has a plural form (cans) and can be modified by adjectives (a dented can). It’s a physical object you can touch, kick, or recycle.
There is also the slang aspect. In some dialects, "the can" refers to the bathroom or even prison. While informal, these are still nouns. If you’re writing a formal essay, maybe skip the prison reference, but keep in mind that the part of speech remains the same: a person, place, or thing.
The "Regular" Verb: Canning and Preserving
Now, let's get even weirder. There is a third way to use this word.
You can "can" something. This is a transitive verb, meaning it takes a direct object. Unlike the modal helper "can," this one is a "regular" verb. It changes based on tense.
- "She cans tomatoes every summer." (Present tense)
- "We canned forty jars of pickles." (Past tense)
- "They are canning the fruit now." (Present participle)
In this scenario, you aren't talking about ability. You’re talking about the act of preserving food in a container. It’s a specific, physical action. It’s also used in business slang to mean firing someone. "The manager canned the new guy for being late." Again, that’s a regular verb usage.
Breaking Down the Syntax
Let's look at how this actually functions in a sentence structure. If you’re a student or someone obsessed with grammar, you might be familiar with sentence diagramming.
When "can" is a modal verb, it sits right next to the main verb in the predicate. In the sentence "You can win," "can win" is the entire verb phrase. "Win" is the head of that phrase, and "can" is the auxiliary.
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When it’s a noun, it usually follows an article (a, an, the) or a possessive. "Look at the can." Or, "That is my can."
When it’s the regular verb meaning to preserve, it follows the standard rules of any other action word like "jump" or "bake."
It’s honestly kind of wild how one three-letter word can jump between these categories so effortlessly. Most of us do it without thinking, but when you’re trying to figure out what parts of speech is can, the context is your only map.
Common Pitfalls and the "Can vs. May" Debate
We have to talk about the permission thing. Your third-grade teacher likely corrected you when you asked, "Can I go to the bathroom?"
"I don't know, can you?" they’d smirk.
The traditional rule is that "can" refers to ability (I am physically able to walk to the bathroom) and "may" refers to permission (I have the authority to go). However, language evolves. The Oxford English Dictionary and most modern linguists acknowledge that "can" is now perfectly acceptable for permission in all but the most formal settings.
Using "can" for permission is a functional shift that has been happening for centuries. If you’re writing a legal brief, stick to "may." If you’re texting a friend, "can" is just fine. Don't let the pedants get you down; the part of speech (modal verb) remains the same regardless of whether you're talking about ability or permission.
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Why This Matters for Your Writing
You might be thinking, "Who cares?"
Understanding what parts of speech is can actually helps you avoid "wordiness" and "passive voice" issues. Because "can" is a modal verb, it often gets overused in business writing. People write "We can provide a solution" when they could just say "We provide a solution."
One sounds like a possibility; the other sounds like a fact.
By identifying "can" as a helper, you can decide if the sentence actually needs help. Sometimes, the main verb is strong enough to stand on its own. On the flip side, knowing when it’s a noun helps you avoid "garden path sentences" where the reader gets confused by a word that could be two different things.
- "The prime minister cans his staff."
Is he preserving them in jars? Or is he firing them? Without the context of "can" as a regular verb vs. the noun or modal, the sentence is a mess.
Putting Knowledge Into Practice
If you want to improve your grammar or just win a bar bet about linguistics, here are the actionable takeaways for identifying this word:
- Check for a partner. If "can" is followed by another verb (like run, jump, think), it’s a modal auxiliary verb.
- Look for an article. If you see "a can" or "the can," it’s a noun. No exceptions here.
- Test the tense. Try to make it past tense. If you can change it to "canned," you are using the regular verb meaning to preserve or fire. If the past tense is "could," you are back in the modal verb territory.
- Watch your tone. Use "can" for ability in formal writing, but feel free to use it for permission in conversational contexts.
- Simplify. In your own writing, look for "can" and see if removing it makes the sentence stronger. "I can see the moon" is often less powerful than "I see the moon."
Next time you see this word, take a second to categorize it. It's a small mental exercise that builds a much deeper understanding of how English actually functions under the hood. Stop viewing words as static definitions and start seeing them as tools that change shape based on where you put them.