Possessive Nouns Can Do Something Strange

Possessive Nouns Can Do Something Strange

Today, I'm answering a reader's question about possessive nouns.


I’ve come across this situation a few times, and I can’t find an explanation. 

I can't find my mom's keys. 

What is “my?" It seems to be an adjective modifying another adjective ("mom's"), but since that’s not possible, is there another term for it? Or would we consider “my mom's” some sort of compound adjective modifying the noun “keys” and leave it at that? I’m intrigued, and any help is appreciated!


Elyse, English Teacher

That's a great question! Before we dive deeper into Elyse's question, let's have a quick review of what nouns and adjectives are. 

Quick Refresher

Nouns name people, places, things, or ideas.

Adjectives modify nouns and pronouns.

Possessive Nouns

Possessive nouns are nouns that show ownership. (You can also think of them as showing possession.)

Mom's keys, lady's books, building's doorbell

The keys belong to Mom, the books belongs to the lady, and the doorbell belongs to the building.

I can't find Mom's keys.

Mom's is a possessive noun. It's telling us whose keys we're talking about.

Mom's is functioning as an adjective modifying the noun keys

Isn't that strange? It's not functioning as a noun. It's functioning as an adjective!

Possessive nouns function as adjectives.

We even diagram these nouns as adjectives. (That means they go under the noun that they are modifying.)

Sentence diagram possessive noun

I can't find Mom's keys!

The Curveball

Check out the sentence below and focus on the word my.

I can't find my mom's keys!

What is my modifying? 

You might be confused because my is an adjective, but it doesn't seem to be modifying the noun keys. After all, they are not my keys, they are my mom's keys. 

My seems to be modifying mom's, and mom's is functioning as an adjective. But wait! Adjectives don't modify other adjectives! What is going on here? 

Sentence diagram possessive noun

Where do we diagram my? What is it doing?

The Trick

The trick is that these kinds of nouns can be modified by adjectives. Even though they function as adjectives, they maintain some of their "noun-ness" and can still be modified by adjectives.

Diagram my on a slanted line under mom's. It will look just like an adverb, but since you're smart, you'll remember that it's actually an adjective modifying a possessive noun. 

Sentence diagram

I can't find my mom's keys.

The Moral of the Story

My is modifying mom's, so it's an adjective modifying an adjective! The trick is to think of mom's as a possessive noun that maintains some of its "noun-ness" even though it's acting as an adjective. It's "noun-ness" makes it able to be modified by adjectives. Diagram my under mom's

There you go. Now you know that these kinds of nouns function as adjectives, but they can also be modified by adjectives. Crazy!

This is original content from https://www.english-grammar-revolution.com/possessive-nouns.html

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Other Helpful Resources

  • Learn more about how to form these nouns, you can read more on this website.