Stem-Changing Verbs o→ue: poder, dormir

In a regular verb, the stem stays the same. Only the ending changes. In a stem-changer, the middle of the word changes too. For poder and dormir, the letter o turns into ue. This happens in almost every form. Why does this happen? It is mostly about the rhythm of the language. Spanish loves a good flow. The ue sound is easier to emphasize in certain spots. Imagine the o is a bit shy. When it gets the spotlight, it brings a friend along. That friend is the letter u. Together, they make the ue sound. It sounds like "way" in English. So poder becomes puedo. And dormir becomes duermo. It is like a grammar dance move. You just have to learn the steps.

1. 1To conjugate these verbs, follow these simple steps:
2. 2Start with the infinitive like poder or dormir.
3. 3Remove the ending (-er or -ir). Now you have the stem: pod- or dorm-.
4. 4Change the o in the stem to ue. Now you have pued- or duerm-.
5. 5Add your regular endings for -er or -ir verbs.
6. 6STOP! Do not change the stem for nosotros or vosotros.
7. 7Let's look at poder (to be able to):
8. 8Yo puedo (I can)
9. 9Tú puedes (You can)
10. 10Él/Ella/Usted puede (He/She/You formal can)
11. 11Nosotros podemos (We can - No change!)
12. 12Vosotros podéis (You all can - No change!)
13. 13Ellos/Ellas/Ustedes pueden (They/You all can)
14. 14See the pattern? If you draw a line around the forms that change, it looks like a boot. The nosotros and vosotros forms stay outside the boot. They are the "ankle" of the leg. They are too strong to change.

Use poder whenever you talk about ability or permission. Are you at a job interview? Use puedo to list your skills. "I can speak three languages." Are you at a restaurant? Use puede to ask for the bill. "Can you bring the check?" It is the ultimate polite tool. It makes you sound helpful and capable.

Use dormir for anything related to sleep. Use it to talk about your habits. "I sleep eight hours every night." Or use it to talk about your pets. "My dog sleeps on the sofa." It is a cozy verb. It is essential for daily conversation. Imagine trying to explain why you are tired without it! It would be a nightmare.

There are two big "No-Go" zones for the o to ue change. These are the nosotros (we) and vosotros (you all in Spain) forms. In these cases, the o stays an o. It is like a grammar traffic light. The light is red for these two forms.

• Correct: Nosotros podemos (We can).
• Incorrect: Nosotros puedemos (This sounds very strange to a native ear).
• Correct: Nosotros dormimos (We sleep).
• Incorrect: Nosotros duermimos (Nope, don't do it!).

Why? Because the stress of the word falls on the ending, not the stem. The o doesn't need the extra u friend when it isn't in the spotlight. Think of nosotros as the "boring but stable" part of the family.

One common mistake is over-correcting. You might start changing every o you see. Not every verb is a stem-changer! Comer (to eat) stays como, not cuemo. Stick to the specific list of stem-changers you learn.

Another mistake is forgetting the change in the ellos/ellas form. People often remember yo puedo but forget ellos pueden. Remember, the boot includes the bottom row!

Finally, watch out for the spelling of dormir in the nosotros form. Since it is an -ir verb, the ending is -imos. Many people accidentally use -emos. It is dormimos, not dormemos. Yes, even native speakers mess this up when they are tired. The irony!

How is this different from other verbs? Regular verbs like beber (to drink) are predictable. Yo bebo, tú bebes. No surprises there. Stem-changers are like regular verbs with a little spice.

You might also see e to ie stem-changers like querer (to want). They follow the exact same "boot" rule. The only difference is which vowel is changing. If you master the boot for poder, you have mastered it for dozens of other verbs. It is a "buy one, get ten free" deal in the grammar world.