Introducir in the Preterite Tense
Introducir means “to introduce, to insert”, and this page covers exactly one thing: introducir in the preterite tense. The preterite is the tense Spanish speakers reach for when they talk about what is finished and done. On this page you will find the full preterite table for introducir, how the tense is formed for this verb, the situations where it is used, how it differs from the imperfect, worked examples, the mistakes learners make most often, an eight-question quiz with explained answers, and answers to the questions students ask about introducir in the preterite. For example: “Ayer, yo introduje la moneda en la máquina.” — Yesterday, I introduced the coin into the machine. Everything on this page uses the forms of introducir exactly as they are conjugated in the preterite, so you can trust every form you see here.
Introducir in the Preterite Tense — full table
| Person | Form |
|---|---|
| yo | introduje |
| tú | introdujiste |
| él/ella/Ud. | introdujo |
| nosotros/as | introdujimos |
| vosotros/as | introdujisteis |
| ellos/ellas/Uds. | introdujeron |
Gerund: introduciendo · Past participle: introducido
The gerund is introduciendo, which you use with estar to say what is happening right now: “Estoy introduciendo” means the action of introducir is in progress at this very moment. The past participle is introducido, which you use with haber in the perfect tenses: “he introducido” is the present perfect, used for a completed action. Keep both forms in mind as you read the examples below, because the preterite is only one part of how introducir is used.
How the preterite of introducir is formed
Introducir does not use one regular stem in this tense, so the forms below do not follow the simple stem + endings pattern. This tense is irregular for this verb: it follows the pattern of the -ducir verbs, with a -zc- in the present (as in traduzco) and a -j- stem in the preterite (as in traduje). Learn the forms in the table rather than guessing them from the infinitive. Learn the six forms as a set: yo introduje, tú introdujiste, él/ella/Ud. introdujo, nosotros/as introdujimos, vosotros/as introdujisteis, ellos/ellas/Uds. introdujeron.
When to use the preterite of introducir
The preterite is not a single-purpose tense. Below are the five situations where you will use introducir in the preterite most often. Each one comes with a real example, so read the rule, then say the example out loud.
1. One finished action
The preterite reports a single action that started and finished in the past. The action is done, counted once, and the story moves on. Example: “Ayer, yo introduje la moneda en la máquina.” — Yesterday, I introduced the coin into the machine.
2. A sequence of events
In a story, each preterite form is one step forward in time. When several things happened one after another, the preterite lists them in order. Example: “Nosotros introdujimos la llave en la cerradura.” — We introduced the key into the lock.
3. A specific time marker
Time words such as ayer, anoche, el año pasado and la semana pasada point to the preterite. They name a finished moment, and the verb must match. Example: “Él introdujo un tema nuevo en la reunión ayer.” — He introduced a new topic in the meeting yesterday.
4. A sudden change or interruption
The preterite describes sudden changes and interruptions: something happened, and the situation was different afterwards. Example: “Ellos introdujeron los datos en el ordenador de repente.” — They introduced the data into the computer suddenly.
5. A completed time frame
When an action took place inside a period of time that is now over, the preterite is the right tense, because the period itself is finished. Example: “Tú introdujiste la moneda en la máquina la semana pasada.” — You introduced the coin into the machine last week.
Preterite Tense vs Imperfect: how to choose
The closest tense to the preterite is the imperfect, and choosing between them is one of the hardest decisions in Spanish. The rule is simple: the preterite reports one finished action, while the imperfect describes background, habits in the past, or an action that was in progress when something else happened. The three pairs below use the same verb, so the only thing that changes is whether the action is finished and counted, or ongoing and descriptive. Time words help: ayer and de repente point to the preterite, while mientras and todos los días in the past point to the imperfect.
Preterite Tense: “Ayer, yo introduje la moneda en la máquina.” — Yesterday, I introduced the coin into the machine.
Imperfect: “Yo introducía la moneda en la máquina cada día.” — I used to introduce the coin into the machine every day.
The preterite sentence reports one finished action; the imperfect sentence describes a habit in the past. Ayer points to the preterite, cada día in the past points to the imperfect.
Preterite Tense: “Anoche, él introdujo la llave en la cerradura.” — Last night, he introduced the key into the lock.
Imperfect: “Él introducía la llave en la cerradura todos los días.” — He used to introduce the key into the lock every day.
Anoche names one finished night, so the preterite is right; todos los días in the past describes a routine, so the imperfect is right.
Preterite Tense: “Nosotros introdujimos un tema nuevo en la reunión ayer.” — We introduced a new topic in the meeting yesterday.
Imperfect: “Nosotros introducíamos un tema nuevo en la reunión cuando éramos jóvenes.” — We used to introduce a new topic in the meeting when we were young.
The preterite sentence counts one finished action; the imperfect sentence describes how things used to be. That difference — finished event versus background — is the whole decision.
Example sentences: introducir in the preterite
Read these eight sentences out loud. They cover all six persons, so by the end you will have seen every form in the table used in a real sentence. Pay attention to the words around the verb — the time expressions, the objects, the other verbs — because those are what make each sentence sound natural.
“Introduje la moneda en la máquina.” — I introduced the coin into the machine.
“Introdujiste la llave en la cerradura.” — You introduced the key into the lock.
“Introdujo un tema nuevo en la reunión.” — He/she introduced a new topic in the meeting.
“Introdujimos los datos en el ordenador.” — We introduced the data into the computer.
“Introdujisteis la moneda en la máquina.” — You introduced the coin into the machine.
“Introdujeron la llave en la cerradura.” — They introduced the key into the lock.
“Introduje un tema nuevo en la reunión.” — I introduced a new topic in the meeting.
“Introdujo los datos en el ordenador.” — He/she introduced the data into the computer.
Common mistakes with introducir in the preterite
These are the errors learners actually make with this verb in this tense. Each one shows the wrong version, the right version, and why the correction matters.
Wrong: “Ellos introdujo la moneda en la máquina.” Right: “Ellos introdujeron la moneda en la máquina.” Why: Ellos needs the ellos form introdujeron. The singular introdujo belongs with él, ella or a singular noun.
Wrong: “Ayer yo introducí la llave en la cerradura.” Right: “Ayer yo introduje la llave en la cerradura.” Why: Introducir has an irregular preterite: the correct first-person form is introduje, not the regular introducí.
Wrong: “Nosotros introdujiste un tema nuevo en la reunión.” Right: “Nosotros introdujimos un tema nuevo en la reunión.” Why: Nosotros needs introdujimos. The tú form introdujiste belongs with tú.
Wrong: “Ellos introduje los datos en el ordenador.” Right: “Ellos introdujeron los datos en el ordenador.” Why: The verb must agree with its subject. Ellos needs the ellos form introdujeron, not the yo form introduje.
Quiz: introducir in the preterite
Choose the correct answer for each question, then check the answer key. Every answer is explained, so a wrong answer still teaches you something.
1. Complete the sentence: “Yo ______ la moneda en la máquina.” (The coin into the machine.)
- (a) introduje
- (b) introdujiste
- (c) introdujo
Answer: introduje — The yo form of introducir in the preterite is introduje. The other options are the forms for different persons, so they do not agree with the subject.
2. Complete the sentence: “¿Tú ______ la llave en la cerradura?” (The key into the lock.)
- (a) introduje
- (b) introdujo
- (c) introdujiste
Answer: introdujiste — The tú form of introducir in the preterite is introdujiste. The other options are the forms for different persons, so they do not agree with the subject.
3. Complete the sentence: “Él ______ un tema nuevo en la reunión.” (A new topic in the meeting.)
- (a) introdujiste
- (b) introdujo
- (c) introduje
Answer: introdujo — The él/ella/Ud. form of introducir in the preterite is introdujo. The other options are the forms for different persons, so they do not agree with the subject.
4. Complete the sentence: “Nosotros ______ los datos en el ordenador.” (The data into the computer.)
- (a) introdujimos
- (b) introduje
- (c) introdujiste
Answer: introdujimos — The nosotros/as form of introducir in the preterite is introdujimos. The other options are the forms for different persons, so they do not agree with the subject.
5. What is the vosotros/as form of introducir in the preterite?
- (a) introduje
- (b) introdujiste
- (c) introdujisteis
Answer: introdujisteis — From the table above: vosotros/as takes introdujisteis. Say it with the example sentence “Vosotros introdujisteis la moneda en la máquina.” to fix it in your memory.
6. Complete the sentence: “Ellos ______ la llave en la cerradura.” (The key into the lock.)
- (a) introdujiste
- (b) introdujeron
- (c) introduje
Answer: introdujeron — The ellos/ellas/Uds. form of introducir in the preterite is introdujeron. The other options are the forms for different persons, so they do not agree with the subject.
7. Which is the correct yo form of introducir in the preterite?
- (a) introduje
- (b) introdujiste
- (c) introdujo
Answer: introduje — The yo form is introduje. The other two options are the forms for other persons.
8. Which sentence describes one finished action in the past?
- (a) Yo introducía la moneda en la máquina cada día.
- (b) Mañana, yo introduciré la moneda en la máquina.
- (c) Ayer, yo introduje la moneda en la máquina.
Answer: Ayer, yo introduje la moneda en la máquina. — “Ayer, yo introduje la moneda en la máquina.” reports a single completed event, so it takes the preterite. The second option describes background or a past habit, and the third looks to the future.
Frequently asked questions
Is introducir regular in the preterite?
No. Introducir has an irregular preterite: introduje, introdujiste, introdujo, introdujimos, introdujisteis, introdujeron. Learn these forms as a set rather than deriving them from the infinitive.
What is the past participle of introducir?
The past participle is introducido: 'He introducido' means 'I have introduced'. It is used with haber in every perfect tense. The gerund is introduciendo.
When do I use the preterite instead of the imperfect for introducir?
Use the preterite for one finished action, as in Ayer, yo introduje la moneda en la máquina. Use the imperfect for a repeated habit or background, as in Yo introducía la moneda en la máquina cada día. The time words around the verb usually tell you which one fits.
How do I remember the preterite forms of introducir?
Say the six forms out loud in order, three times, with a real sentence for each one: yo introduje, tú introdujiste, él/ella/Ud. introdujo, nosotros/as introdujimos, vosotros/as introdujisteis, ellos/ellas/Uds. introdujeron. Then write three of your own sentences with introducir in the preterite, using the examples on this page as models.
Related pages
- Full conjugation of introducir — every tense of introducir in one place.
- Introducir examples and quiz — more sentences with introducir and a ten-question quiz.
- Spanish preterite guide — how the preterite works for all Spanish verbs.
- Spanish verbs — the hub for every Spanish verb on VerbFlow.
- Preterite conjugator — conjugate any verb in the preterite instantly.
- Verb quiz — test yourself on introducir and other verbs.