Preterite Regular ER/IR Verbs: comí, comiste...

In Spanish, verbs change their endings to show who did the action. In the preterite, these endings also show the action is over. For regular -er and -ir verbs, the process is identical. You take the base of the verb. You add a specific ending based on the person. It is like a plug-and-play system. You don't need to worry about different patterns for comer and vivir. They are grammatical twins in this tense. This makes the preterite much easier than the present tense. In the present, these two groups often diverge. Here, they are united. It is like a grammar peace treaty. Just remember the six specific endings. Once you have those, you can conjugate hundreds of verbs instantly.

1. 1Ready to build some verbs? Follow these three simple steps. We will use comer (to eat) and abrir (to open) as our models.
2. 2Start with the infinitive verb. For example, comer.
3. 3Remove the last two letters (-er or -ir). Now you have the stem: com-.
4. 4Add the preterite endings to the stem:
5. 5yo: -í (comí)
6. 6tú: -iste (comiste)
7. 7él/ella/usted: -ió (comió)
8. 8nosotros/nosotras: -imos (comimos)
9. 9vosotros/vosotras: -isteis (comisteis)
10. 10ellos/ellas/ustedes: -ieron (comieron)
11. 11Notice the accents on the yo and él/ella forms. These are vital. Without them, the word might mean something else entirely. Or it might not be a word at all. Think of the accent as the "past tense hat." It needs to be worn to look right.

Use the preterite when an action is a completed event. It is for things that happened at a specific time.

• One-time events: Ayer comí pizza. (Yesterday I ate pizza.)
• Specific time frames: Viví en Madrid por dos años. (I lived in Madrid for two years.)
• A list of actions: Me desperté, bebí café y salí. (I woke up, drank coffee, and left.)
• Interruptions: Yo dormía cuando el teléfono sonó. (I was sleeping when the phone rang.)

Imagine you are a movie director. The preterite is for the "cuts" and the "actions." It moves the plot forward. If you can put a specific date or time on it, use the preterite. It is great for job interviews too. "I worked there for three years." "I learned new skills."

Don't use the preterite for background descriptions. That is a different job.

• Habits: If you "used to" do something, don't use this.
• Descriptions: Saying "the house was big" requires the imperfect tense.
• Ongoing states: Feelings or mental states usually use the imperfect.
• Weather: Saying "it was sunny" is usually background info.

Think of the preterite as a camera flash. It captures a single, bright moment. If you want to describe the whole party atmosphere, use the imperfect. Using the preterite for a habit sounds like it only happened once. It might confuse your listener. "I went to the gym" (once) vs "I used to go to the gym" (habit).

Everyone makes mistakes, even native speakers sometimes! Here are the big ones to watch out for.

• Missing Accents: Writing comio instead of comió. The accent changes the stress. Without it, you sound like a robot.
• Confusing with -AR: Don't use -é for yo with -er verbs. Comé is wrong. It must be comí.
• The "Nosotros" Trap: For -ir verbs, the past and present are the same. Vivimos can mean "we live" or "we lived." Use context clues like ayer to help.
• Overusing it: Don't try to use it for everything in the past. If you're describing a scene, switch gears. It’s a common trap for English speakers.

The biggest contrast is with the Present Tense.

• Present: Como (I eat). Preterite: Comí (I ate).
• Present: Vive (He lives). Preterite: Vivió (He lived).

Also, compare it to the Preterite of -ar verbs.

• -ar verbs use -é and -ó.
• -er/-ir verbs use -í and -ió.

Notice that the él/ella form for both ends in o with an accent. That is a helpful pattern to memorize. If you see an o with an accent at the end of a verb, it’s almost always the past tense. It's like a grammar lighthouse guiding you home.