Prepositions that change verb meanings
A small word after a verb can change its meaning completely: deber (should) but deber de (must be), acabar (finish) but acabar de (have just).
The rule at a glance
verb + preposition = a new verb
Learn each verb with its preposition
deber de: supposition
debe de
must be (probably)
Debe de ser tarde.
It must be late / It's probably late.
pensar en: think about
pienso en
I think about
Pienso en ti todo el día.
I think about you all day.
acabar de: have just
acabo de
I've just
Acabo de llegar.
I've just arrived.
contar con: count on
contar con
to count on
Puedes contar conmigo.
You can count on me.
The five verbs
Adding or changing a preposition after a verb can completely alter its meaning: en, de, con or a can turn a verb into something entirely different. English speakers often struggle with these because we think of verbs and prepositions separately; in Spanish, verb + preposition combinations work as distinct verbs with their own meanings. This page covers five essential verbs: deber, pensar, acabar, contar and quedar.
| Verb | On its own | With a preposition (or se) |
|---|---|---|
| deber | should, ought to (obligation) | deber de: must be, probably (supposition) |
| pensar | to think, to believe; to plan to | pensar en: to think about · pensar de: to think of (opinion questions) |
| acabar | to finish, to end | acabar de: to have just done · acabar con: to put an end to, to finish off |
| contar | to count / to tell | contar con: to count on / to have available |
| quedar | to remain, to be left / to be located / to fit | quedar con: to meet (someone) · quedar en: to agree to · quedarse: to stay |
When to use each
1. Deber vs deber de
Deber + infinitive expresses obligation, duty or advice. For supposition or probability, deber de + infinitive is the recommended form; deber + infinitive is also widely used and accepted with that meaning (Debe ser tarde), and context tells you which is meant. What to avoid is deber de for obligation.
Obligation: Debes estudiar más. You should study more.
Obligation: Debemos ser honestos. We should be honest.
Supposition: Debe de ser tarde. It must be late / It's probably late.
Supposition: Debe de haber un problema. There must be a problem.
2. Pensar, pensar en, pensar de
Pensar: to think, to believe (and, with an infinitive, to plan to). Pensar en: to have someone or something in your thoughts. Pensar de is mainly for questions asking for opinions; in answers, use pensar que.
pensar: Pienso que tienes razón. I think you're right.
pensar + infinitive: Pienso viajar a España. I plan to travel to Spain.
pensar en: Pienso en cambiar de trabajo. I'm thinking about changing jobs.
pensar de: ¿Qué piensas de mi idea? What do you think of my idea?
3. Acabar, acabar de, acabar con
Acabar: to finish, to end. Acabar de + infinitive: a recent past action. Use the present tense for "have just" and the imperfect for "had just".
acabar: Acabé el libro ayer. I finished the book yesterday.
acabar de: Acabo de llegar. I've just arrived.
acabar de: Acabamos de comer. We've just eaten.
acabar con: Hay que acabar con la pobreza. We must end poverty.
4. Contar vs contar con
Contar: counting numbers or telling stories. Contar con: relying on someone, or having resources.
contar: El niño cuenta hasta diez. The child counts to ten.
contar: Cuéntame qué pasó. Tell me what happened.
contar con: Puedes contar conmigo. You can count on me.
contar con: Contamos con buenos recursos. We have good resources.
5. Quedar, quedar con, quedar en, quedarse
Quedar: to remain, to be located, or how something fits; in Spain also to meet up. Quedar con: to meet someone. Quedar en: making arrangements or agreements. Quedarse (reflexive): actively staying in a place, or keeping something.
quedar: Quedan dos días. Two days remain / are left.
quedar: ¿Dónde queda el museo? Where is the museum?
quedar con: He quedado con Ana a las ocho. I'm meeting Ana at eight.
quedar: ¿Quedamos a las ocho? Shall we meet at eight?
quedar en: Quedamos en vernos mañana. We agreed to see each other tomorrow.
quedarse: Me quedo en casa. I'm staying at home.
More set phrases like acabar de + infinitive are in Spanish verbal phrases. For obligation, see modal verbs compared: deber vs tener que vs haber que.
Common mistakes
Using deber de for obligation
Not this (incorrect): Debes de estudiar más (meaning "you should")
But this (correct): Debes estudiar más – You should study more. For obligation, use deber without de. Deber de is for probability (where deber alone is also accepted).
Pensar en, not pensar de or sobre
Not this (incorrect): Pienso de ti todo el día
But this (correct): Pienso en ti todo el día. To have someone in your thoughts is pensar en; pensar de only asks for an opinion (¿Qué piensas de...?).
Wrong tense with acabar de
Not this (incorrect): Acabé de comer (for "I've just eaten")
But this (correct): Acabo de comer. Use the present tense for "just" actions.
Forgetting "con" with contar
Not this (incorrect): Puedes contar en mí
But this (correct): Puedes contar conmigo. Always use "con" (not "en") for "count on".
Confusing quedar and quedarse
Not this (incorrect): Quedo en casa (for staying at home)
But this (correct): Me quedo en casa. Use reflexive "quedarse" for actively staying.
Quick check
6 questions1. Son las doce. Los niños ___ estar durmiendo. (I assume they are)
Deber de + infinitive is the recommended form for supposition (deben estar is also accepted).
2. Siempre pienso ___ mi familia.
Pensar en: to think about someone.
3. "I've just arrived" is...
Acabar de in the present tense for "have just".
4. Puedes contar ___ para la mudanza.
Contar con: to count on. Con + mí = conmigo.
5. Hoy no salgo: ___ en casa.
Quedarse: to stay somewhere.
6. ¿Qué piensas ___ la película?
Pensar de in questions asking for an opinion.
Pick the verb or preposition that fits.
Going further
Deber vs deber de side by side, and more examples in context
Deber vs deber de: quick comparison
It's 11 pm: Los niños deben estar durmiendo. The children should be sleeping (obligation), or, from context, they must be sleeping: deber alone is also accepted for probability.
It's 11 pm: Los niños deben de estar durmiendo. The children must be sleeping (I assume they are, based on the time).
A guess: Debe de tener unos 40 años. He/She must be around 40 years old (my guess).
More examples in context
Late night conversation
Deberías ir a casa, es tarde. You should go home, it's late (advice).
Debe de ser medianoche ya. It must be midnight already (supposition).
No contaba con que fuera tan tarde. I wasn't expecting it to be so late.
Making plans
Pienso ir al cine este fin de semana. I plan to go to the cinema this weekend.
Pienso en qué película ver. I'm thinking about which film to watch.
Quedamos en vernos a las ocho. We agreed to meet at eight.
After dinner
Acabo de comer. I've just eaten.
Acabamos con todo el postre. We finished off all the dessert.
Me quedo un rato más. I'm staying a bit longer.
Work conversation
Puedes contar conmigo para el proyecto. You can count on me for the project.
Contamos con poco presupuesto. We have a small budget.
Quedan tres semanas para terminar. Three weeks remain to finish.
More with each verb
Pienso en ti todo el día. I think about you all day.
¿Qué piensas de la película? What do you think of the film?
Acabé comprando dos. I ended up buying two.
Acabamos con toda la comida. We finished off all the food.
No contaba con que llegaras. I wasn't expecting you to arrive.
Esta camisa me queda bien. This shirt fits me well.
Quedamos en que tú pagas. We agreed that you would pay.
Me quedo con este. I'll take this one.
Me quedé sorprendido. I was surprised (ended up surprised).
Pienso que la película es buena. I think the film is good (not: Pienso de la película que es buena).