The Infinitive as a Noun and After Prepositions

There is one mistake English learners of Spanish make more than any other, and it is not a matter of vocabulary or accents. It is the -ing form. In English, when an action behaves like a noun - smoking is bad, before leaving, without thinking, on arriving - we end it in -ing. So learners go looking for a Spanish -ing to match, and reach for the gerund: fumando, saliendo, pensando. It is wrong nearly every time.

Where English uses the noun-like -ing, Spanish uses the plain infinitive - the dictionary form ending in -ar, -er or -ir. The infinitive is not just a verb waiting to be conjugated. It is Spanish's verbal noun: it names the action, it works as a subject, and it slots in after every preposition. Learn that one fact and a whole category of errors disappears.

The infinitive as a noun

An infinitive can be the subject of a sentence - the thing the sentence is about - exactly where English would use the -ing form.

• Fumar es malo. (Smoking is bad.)
• Nadar es mi deporte favorito. (Swimming is my favourite sport.)
• Viajar abre la mente. (Travelling opens the mind.)
• Aprender idiomas es útil. (Learning languages is useful.)

Notice there is no -ando or -iendo anywhere. The subject is the bare infinitive, and the verb that follows it is singular, because a nominalised infinitive counts as a masculine singular noun.

You can also put the article el in front, which makes the action sound a touch more abstract or weighty - common in general truths and headlines.

• El comer bien es importante. (Eating well is important.)
• El fumar perjudica la salud. (Smoking harms your health.)
• El viajar cuesta dinero. (Travelling costs money.)

The el is optional. Comer bien es importante is just as correct and slightly more everyday. But when you do use an article, it is always el - masculine, singular, whatever the verb. You would never write la comer or try to make it plural.

The infinitive after prepositions

This is the big one. After every preposition, Spanish uses the infinitive where English uses the -ing form. There are no exceptions to hunt for.

Some of these in full sentences:

• Antes de salir, cierra la puerta. (Before leaving, close the door.)
• Después de comer, dormimos la siesta. (After eating, we have a nap.)
• Se fue sin decir nada. (He left without saying anything.)
• Estudio para aprobar el examen. (I study in order to pass the exam.)
• En vez de trabajar, se quedó en la cama. (Instead of working, he stayed in bed.)
• Además de ser guapo, es simpático. (Besides being handsome, he is nice.)

Every single one uses the infinitive. Say antes de saliendo or sin pensando and you have marked yourself as a beginner in three words. The rule is watertight: preposition + infinitive, never preposition + gerund.

al + infinitive: "on / upon doing" or "when"

There is one preposition-plus-infinitive combination worth its own section, because it does something English handles with a whole clause. Al (the contraction of a + el) followed by an infinitive means "on" or "upon" doing something, or simply "when" it happens. It ties one action to the exact moment of another.

• Al llegar a casa, me quité los zapatos. (On arriving home, I took off my shoes.)
• Al verla, sonrió. (On seeing her, he smiled.)
• Al oír la noticia, se puso a llorar. (On hearing the news, she burst into tears.)
• Al abrir la puerta, noté el frío. (When I opened the door, I felt the cold.)

The clever part is that al + infinitive carries no tense of its own - it borrows its timing from the main verb. Al salir can mean "when I leave", "when I left" or "when I will leave", entirely depending on the surrounding sentence. It is far more compact than a full cuando clause, and much more natural in speech: al terminar, te llamo (when I finish, I'll call you) beats the wordier cuando termine, te llamo for a quick, simultaneous action.

After verbs, too

The infinitive is also the form that follows another conjugated verb directly - quiero comer (I want to eat), puedo ir (I can go). And crucially, after gustar and its relatives, the thing you like is expressed as an infinitive, not a gerund.

• Me gusta nadar. (I like swimming.) Never me gusta nadando.
• Nos encanta viajar. (We love travelling.)
• Le molesta esperar. (Waiting annoys him.)

English "I like swimming" fools learners into me gusta nadando constantly. It is me gusta nadar: the infinitive naming the activity you enjoy.

Where the gerund actually belongs

To keep the line clear: the Spanish gerund (hablando, comiendo, viviendo) has real jobs, just not these ones. It describes an action in progress, usually with estar - estoy comiendo (I am eating) - or works like an adverb - salió corriendo (he ran out). Those are separate topics. The moment an action needs to behave like a noun - as a subject, or after a preposition - the gerund steps aside and the infinitive takes over.

Common mistakes English speakers make

Translating the noun-like -ing with a gerund. "Smoking is bad" becomes fumando es malo in the learner's head; it is fumar es malo. Any -ing that works as a subject is an infinitive in Spanish.

Using the gerund after a preposition. Antes de saliendo, sin pensando, después de comiendo are all wrong. After a preposition the form is invariably the infinitive: antes de salir, sin pensar, después de comer.

Saying me gusta nadando. After gustar, encantar and friends, the activity is an infinitive: me gusta nadar, le encanta cantar. The gerund never appears here.

Forgetting that al means "on/when". Learners read al llegar as "to the arrive" and freeze. It is a fixed construction: al + infinitive = "on doing / when doing", with its tense borrowed from the main verb.

Get these two uses right - the infinitive as a noun, and the infinitive after prepositions - and you will already sound markedly less like a translated Englishman. When in doubt and an -ing is tugging at you, reach for the infinitive first.

See also

• The present progressive with estar - where the gerund does belong: describing an action in progress right now.
• The adverbial gerund - the gerund's other job, working like an adverb alongside another verb.
• Verbs with prepositions - many of these verbs are followed by an infinitive: insistir en saber, dejar de fumar, empezar a llover.
• The Spanish grammar cheatsheet has the infinitive-after-prepositions rule and the al + infinitive pattern on one card.