Every Portuguese infinitive can be dressed up as a noun simply by placing the definite article o in front of it. O fumar ("smoking"), o comer ("eating"), o saber ("knowledge"), o beber ("drinking"), o andar ("walking"). The article does all the grammatical work: it turns the infinitive from a verbal form — something that names an action — into a noun — something that names a thing, abstract though that thing may be. This is the closest Portuguese comes to English gerund-as-noun ("smoking is bad," "dancing is fun"), and the grammatical mechanism is entirely different.
This page is about the nominalized infinitive: when Portuguese uses it, what it means, and how it differs from the bare verbal infinitive. At the edge of the topic are a handful of infinitives that have fully lexicalized — become dictionary nouns in their own right — like o jantar ("dinner"), o olhar ("gaze, look"), and o andar ("floor of a building"). These are worth knowing separately because they behave like ordinary nouns, not verbs under a nominalizing article.
The construction: article + infinitive
The formula is strikingly simple. Take any infinitive, prefix it with o (or the appropriate article form), and you have a noun phrase. The result is masculine, singular, and abstract — it denotes the activity or the concept, not a specific instance.
O fumar faz mal à saúde.
Smoking is bad for your health.
O estudar exige paciência e dedicação.
Studying requires patience and dedication.
O saber não ocupa lugar.
Knowledge takes up no space. (a well-known proverb)
In each of these, o fumar, o comer, o estudar, o saber are noun phrases — they can be subjects, objects of prepositions, or the complement of a copula. They behave syntactically like any other noun phrase in the language.
When to use the nominalized infinitive
Portuguese has several ways to talk abstractly about an activity. The nominalized infinitive is one of them, and it competes with two alternatives: the bare infinitive (no article) and abstract deverbal nouns (like o estudo "the study," a leitura "the reading").
Option 1: bare infinitive as subject (no article)
In impersonal statements, Portuguese often uses the bare infinitive as subject — no article needed:
Fumar faz mal à saúde.
Smoking is bad for your health. (bare infinitive — the more common construction)
Estudar todos os dias é essencial.
Studying every day is essential.
Aprender uma língua nova abre portas.
Learning a new language opens doors.
This is the everyday, neutral way of saying it. In most contexts, a Portuguese speaker reaches for the bare infinitive before the article.
Option 2: article + infinitive (nominalized)
The article gives the construction extra nominal weight — it emphasizes the activity as a thing in itself, often in a philosophical, reflective, or slightly emphatic register.
O fumar é um vício difícil de largar.
Smoking is a habit that's hard to quit. (emphasizing smoking as a category)
O beber excessivo destrói famílias.
Excessive drinking destroys families.
Não é o trabalhar que me cansa — é o não descansar.
It's not the working that tires me out — it's the not resting.
The presence of o makes the construction feel more topical, more emphatic, or more literary. A self-help book might say fumar faz mal; a philosophical essay is more likely to say o fumar é uma forma de evasão. Both are grammatical; they differ in tone.
Option 3: a dedicated deverbal noun
Many verbs have a corresponding noun that names the same activity without needing any infinitive machinery:
| Verb | Nominalized infinitive | Deverbal noun |
|---|---|---|
| estudar | o estudar | o estudo |
| ler | o ler | a leitura |
| escrever | o escrever | a escrita |
| cantar | o cantar | o canto |
| dançar | o dançar | a dança |
| beber | o beber | a bebida (a drink), a bebedeira (drunkenness) |
The deverbal noun is usually the default choice in neutral prose — os estudos, a leitura, a dança are everyday words. The nominalized infinitive is reserved for when the speaker wants to emphasize the activity as a process or a category, rather than reach for an existing lexical noun.
A leitura é um dos meus passatempos favoritos.
Reading is one of my favorite hobbies. (deverbal noun — neutral)
O ler em voz alta ajuda a memorizar.
Reading aloud helps memorization. (nominalized infinitive — emphatic)
The nominalized infinitive with modifiers
Once you have turned an infinitive into a noun with o, you can modify it like any other noun. Adjectives, prepositional phrases, and quantifiers all work.
O comer rápido faz mal à digestão.
Eating quickly is bad for digestion.
O falar constante dela irrita os colegas.
Her constant talking annoys her colleagues.
O dormir pouco afeta o humor no dia seguinte.
Sleeping little affects your mood the next day.
O meu andar apressado chama sempre a atenção.
My hurried walking always draws attention.
Note that these modifiers (adverbs like rápido, constante, apressado) behave as if they were modifying a noun, not a verb. Technically rápido here could be parsed as an adverb modifying the verb comer inside the nominalization, or as an adjective modifying the resulting noun — Portuguese grammar allows both analyses, and the effect is the same.
The nominalized infinitive after prepositions
One place the nominalized infinitive is particularly common: after a preposition, when the speaker wants to talk abstractly about the activity.
Estou cansado do estudar sem parar.
I'm tired of studying nonstop.
Aprendi muito com o trabalhar em equipa.
I learned a lot from working on a team.
O segredo está no praticar todos os dias.
The secret is in practicing every day.
Ganhei disciplina através do estudar regular.
I gained discipline through regular studying.
Notice the preposition contractions: de + o = do (do estudar), em + o = no (no praticar), a + o = ao. These are the normal Portuguese article contractions; they apply just the same when the article is part of a nominalized infinitive.
Be careful not to confuse ao + infinitive (temporal: "upon doing, when doing") with a + o + infinitive as article + nominal. They overlap in form but have very different meanings:
Ao entrar na sala, cumprimentei toda a gente.
Upon entering the room, I greeted everyone. (temporal ao)
O meu cumprimento ao entrar foi frio.
My greeting on entering was cold. (here ao = 'on, at the time of', still mostly temporal)
In practice, ao + infinitive is almost always read as temporal. The pure nominalization after a is rare; it is far more common with de, em, por, com.
Lexicalized noun-infinitives: o jantar, o olhar, o andar
A separate phenomenon is the set of infinitives that have been fully lexicalized — absorbed into the Portuguese lexicon as dictionary nouns. These are no longer perceived as verbs-dressed-as-nouns; they are just nouns, with their own stable meanings that often differ from (or narrow) the verbal meaning.
The major lexicalized noun-infinitives:
| Noun | Meaning | Corresponding verb |
|---|---|---|
| o jantar | dinner (the meal) | jantar (to have dinner) |
| o almoço | lunch (the meal) | almoçar (to have lunch) — unrelated noun form |
| o olhar | the gaze, the look | olhar (to look) |
| o andar | floor (of a building); walk, gait | andar (to walk) |
| o ser | a being, an entity | ser (to be) |
| o poder | power, authority | poder (to be able to) |
| o dever | duty, obligation | dever (must, ought to) |
| o prazer | pleasure | prazer — archaic verb, now noun-only |
| o parecer | opinion, view | parecer (to seem) |
| o saber | knowledge | saber (to know) |
| o amanhecer | dawn, daybreak | amanhecer (to dawn) |
| o anoitecer | nightfall, dusk | anoitecer (to become night) |
| o cantar | song, the singing | cantar (to sing) |
| o pôr do sol | sunset | pôr (to set/put) |
These can be pluralized, modified with adjectives, and generally used like ordinary nouns:
Os jantares de domingo em casa da avó são sagrados.
Sunday dinners at Grandma's are sacred.
Tem um olhar penetrante.
He has a penetrating gaze.
Vivo no terceiro andar do prédio ao lado do café.
I live on the third floor of the building next to the cafe.
O poder corrompe, e o poder absoluto corrompe absolutamente.
Power corrupts, and absolute power corrupts absolutely.
Cumpro os meus deveres sem reclamar.
I fulfill my duties without complaining.
Foi um prazer conhecer-te.
It was a pleasure to meet you.
Qual é o teu parecer sobre esta proposta?
What's your opinion on this proposal?
O amanhecer sobre o Tejo é de cortar a respiração.
The dawn over the Tagus is breathtaking.
Note that once lexicalized, these nouns are frozen. You cannot re-verb them. O jantar is "dinner"; jantar (the verb) is "to have dinner." They coexist but do not blend:
O jantar estava delicioso.
The dinner was delicious. (noun)
Fomos jantar ao restaurante novo.
We went to have dinner at the new restaurant. (verb)
Depois de jantarmos, fomos ao cinema.
After we had dinner, we went to the cinema. (verb, personal infinitive)
Semantic nuances: what the nominalized infinitive says
The nominalized infinitive almost always conveys one of three things:
The activity as an abstract category. O fumar, o beber, o estudar — the activity considered as a general phenomenon or a lifestyle choice.
The activity as a process or experience. O estar doente ("being sick") — the condition as lived through.
A slightly literary or philosophical tone. Writers and speakers reach for o + infinitive when they want the sentence to feel weighty or reflective.
O ser e o parecer nem sempre coincidem.
Being and seeming don't always coincide.
O envelhecer é inevitável; o amadurecer é opcional.
Aging is inevitable; maturing is optional.
O existir é um verbo ativo, não passivo.
To exist is an active verb, not a passive one.
These feel more reflective or aphoristic than the bare infinitive would. In a newspaper editorial or a philosophy essay, the nominalized form is more likely; in everyday speech, the bare infinitive dominates.
The nominalized infinitive vs the personal infinitive
Do not confuse the nominalized infinitive with the personal infinitive. They look similar at the edges but do entirely different work.
O comer é importante.
Eating is important. (nominalized — abstract activity)
É importante comermos juntos.
It's important for us to eat together. (personal infinitive — specific subject)
The first sentence has o comer as a noun phrase — the article tells you it is abstract. The second sentence has a personal infinitive comermos — the -mos ending tells you the subject is nós. They are not in competition; they answer different questions.
A side-by-side test: can you substitute the noun phrase with a single noun?
- O comer é importante. → A comida é importante. Works — o comer is a noun.
- É importante comermos juntos. → É importante almoços juntos. Does not work — comermos is a verb.
If substitution with a deverbal noun is natural, you are dealing with a nominalized infinitive. If not, you are dealing with a verbal infinitive (bare or personal).
Comparison with English
English has no direct analog. The English gerund (-ing) does this work — smoking is bad, eating as a family is important, reading is one of my hobbies. Portuguese uses the infinitive instead, sometimes with an article, sometimes without.
| English | Portuguese — bare | Portuguese — nominalized |
|---|---|---|
| Smoking is bad for you. | Fumar faz mal. | O fumar faz mal. |
| Reading relaxes me. | Ler relaxa-me. | O ler relaxa-me. |
| Eating late is not healthy. | Comer tarde não é saudável. | O comer tarde não é saudável. |
The bare form is the everyday default. The nominalized form is reserved for emphasis, reflection, or literary register. A learner who always reaches for the article will sound slightly bookish; a learner who never reaches for it will miss a useful register shift.
Comparison with Spanish
Spanish also nominalizes infinitives with el — el fumar, el saber, el comer — and the semantics are almost identical to Portuguese. The famous Spanish proverb el saber no ocupa lugar is the exact calque of Portuguese o saber não ocupa lugar. If you have studied Spanish, this construction transfers one-to-one.
Where Spanish and Portuguese differ is the inventory of lexicalized infinitive-nouns. Portuguese has o jantar for "dinner"; Spanish has la cena. Portuguese has o andar for "floor of a building"; Spanish uses el piso (an unrelated word). These are vocabulary differences, not grammatical ones — the nominalization mechanism is the same.
Common Mistakes
❌ O comermos é importante.
Incorrect — the nominalized infinitive is always bare (no personal-infinitive ending).
✅ O comer é importante.
Eating is important.
✅ É importante comermos juntos.
It's important for us to eat together. (different construction — personal infinitive without article)
The article cannot combine with a personal-infinitive ending. If you want the noun-reading, use o + bare infinitive. If you want the specific-subject reading, drop the article and use the personal infinitive.
❌ Adoro o correr de manhã.
Unusual — after adorar, the bare infinitive is more natural. The article sounds overly formal.
✅ Adoro correr de manhã.
I love running in the morning.
In casual speech, the bare infinitive dominates after main verbs like adorar, gostar de, detestar, preferir. Using the article makes the sentence sound bookish or philosophical, which rarely matches the conversational register.
❌ Ontem comi um bom jantar em casa da minha mãe.
Odd collocation — comi um bom jantar overlaps in meaning. Use jantei or tivemos um bom jantar.
✅ Ontem tivemos um bom jantar em casa da minha mãe.
Last night we had a nice dinner at my mom's.
✅ Ontem jantei muito bem em casa da minha mãe.
Last night I had a really good dinner at my mom's.
O jantar as a noun works with verbs like ter, preparar, comer, servir; jantar as a verb stands on its own. Mixing them (comi um jantar) produces a pleonastic result that native speakers avoid.
❌ O saber uma língua estrangeira abre portas.
Slightly awkward — the bare infinitive is more natural here.
✅ Saber uma língua estrangeira abre portas.
Knowing a foreign language opens doors.
When the infinitive has a direct object (uma língua estrangeira), the bare form is usually smoother. The article tends to be preferred with intransitive or absolute infinitives (o saber, o comer, o estudar) rather than ones with complex complements.
❌ Vivo em terceiro andar.
Missing article — lexicalized o andar (floor) takes a definite article.
✅ Vivo no terceiro andar.
I live on the third floor.
O andar is a fully lexicalized noun and follows normal noun grammar, including the article contractions (em + o = no). This is a small but consistent trap for learners.
Key takeaways
- Any Portuguese infinitive can be nominalized by prefixing the definite article: o fumar, o comer, o saber.
- The construction denotes the activity or concept abstractly, often with emphatic or literary tone.
- In neutral speech, the bare infinitive (no article) is the default choice for gerund-like uses: fumar faz mal, estudar exige paciência.
- A handful of infinitives are fully lexicalized as nouns: o jantar (dinner), o olhar (gaze), o andar (floor), o poder (power), o dever (duty), o parecer (opinion), o saber (knowledge), o amanhecer (dawn). These behave as ordinary nouns.
- The nominalized infinitive is always bare — no personal-infinitive endings. If you need to mark a specific subject, use the personal infinitive instead, without the article.
- After prepositions, the article contracts normally (do estudar, no praticar, com o trabalhar).
Related Topics
- Infinitive After PrepositionsA2 — Portuguese prepositions always take the infinitive — never a conjugated verb. A tour of de, a, para, em, por, sem, até, and ao, with the shift to personal infinitive when the subject matters.
- Infinitive After Other VerbsA1 — When one Portuguese verb is followed by another, the second verb is almost always an infinitive — bare or personal, with or without a linking preposition. A map of modals, aspectual verbs, causatives, and perception verbs.
- Impersonal vs Personal Infinitive: Quick ReferenceB1 — A decision-tree guide to choosing between the bare infinitive and the personal (inflected) infinitive. Same subject, different subject, modal, preposition, impersonal expression, volition — a one-page answer key.
- Personal Infinitive as SubjectB2 — Using the inflected infinitive as the subject of a sentence — é importante estudarmos, é bom vocês virem, lermos ajuda a memorizar — and how this competes with the que + subjunctive construction.
- Personal Infinitive: OverviewB1 — The infinitivo pessoal — an infinitive that conjugates for person and number — is Portuguese's signature grammatical feature, and one of the things that makes the language feel unlike the rest of Romance.