The Ultimate Spanish Indefinite Article User's Manual

Did you know the word “a” is the fifth most commonly used word in English?

You are probably not surprised.

It is hard to get through a sentence without using it.

“A” is called an indefinite article in English, and as you can see above, it is a tiny but powerful little word.

It is no different in Spanish. Understanding the Spanish indefinite articles is crucial to speaking fluently. You will be using them all the time!

Fortunately, Spanish indefinite articles function in a very similar way to the English ones, although there are some important distinctions.

We will walk through all of them in this article. But before entering the realm of my grammar-loving brain, let us see what an indefinite article really is.

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What Is an Indefinite Article?

When we refer to people or things that have not been specifically identified, we need to use an indefinite article. In English, we use the indefinite articles a and an (as opposed to the definite article the). As we will see later on, Spanish has four indefinite articles: un, una, unos, unas.

There is a little trick I always share with my students when studying the indefinite articles in Spanish: in most cases, you should use the indefinite article every time there is at least one person in the conversation that does not already know what or who you are talking about.

Imagine the following situation. Mark and Peter are chatting. Mark has bought a new car and is very eager to share the news.

Mark: ¡Hola, Peter! ¿Sabías que me he comprado un coche nuevo? (Hi, Peter! Did you know I have bought a new car?)

Peter: ¿De verdad? ¿Y qué has hecho con el viejo? (Really? What have you done with the old one?)

Mark: Se lo he vendido a un amigo. (I have sold it to a friend.)

As you can see, when Mark mentions his new car for the first time, he is using the indefinite article both in Spanish and English. Peter had no idea of the existence of the new car, so Mark needs to use the indefinite article to introduce it.

If you have a closer look at the second line of dialogue, you will see the words “el” and “the” are emphasized. Peter is asking about an old car, a car both he and Mark knew about, so instead of using the indefinite article, he uses the definite one.

Finally, Mark’s answer “a un amigo” implies there is a friend of his who bought the old car—something else that Peter did not know about.

Now imagine Sandra is passing by and she sees the guys talking. She is now new to the conversation, so see what happens:

Sandra: Hola, chicos. ¿Qué tal? (Hi, guys. What’s up?)

Peter: Hola, Sandra. Mark se ha comprado un coche nuevo. (Hi, Sandra! Mark has bought a new car.)

Mark: Sí, es el coche que te enseñé ayer. (Yes, it’s the car I showed you yesterday.)

Peter did not know Sandra had already seen the car, so he thinks the fact that Mark has a new car is new information for Sandra. He uses the indefinite article in order to introduce the information. However, Mark has already shown the car to Sandra, so he rectifies Peter indirectly by using “el,” because Sandra already knows what he is talking about.

Later in this post we will explain some different, specific contexts that require the indefinite article, but these are the basic principles you can use going forward.

Un, Una, Unos, Unas! How to Use the Spanish Indefinite Articles Correctly in Any Context

I have divided the following information into different sections.

First you will have a quick overview of the different Spanish indefinite articles with their meanings and some sample sentences for each of them.

Then you will find a section regarding grammatical gender and number and how they work alongside indefinite articles. The final two sections cover the uses of the indefinite article and the situations where you should omit it, respectively.

Get to Know the Spanish Indefinite Articles

Un (A/An)

Un is the masculine, singular indefinite article. That means we use it alongside masculine, singular nouns.

Words like padre, libro, vaso or gato accept un. Have a look:

Soy un padre muy responsable. (I am a very responsible father.)

Tengo un libro rojo. (I have a red book.)

Hay un vaso encima de la mesa. (There is a glass on the table.)

¿Es eso un gato? (Is that a cat?)

Una (A/An)

The exact same thig happens with the article una. It is the feminine, singular indefinite article, so only feminine, singular nouns can accompany it.

Take as an example the words madre, piedra, casa and amiga:

María es una buena madre. (María is a good mother.)

Me he encontrado una piedra en el bolsillo. (I have found a stone in my pocket.)

Hay una casa cerca del lago. (There’s a house near the lake.)

Juana es una amiga mía. (Juana is a friend of mine.)

Unos (Some/A few)

Unos is the masculine, plural indefinite article. So, as you can probably guess by now, it accompanies masculine, plural nouns.

Have a look at some examples:

Hay unos niños en ese parque. (There are some kids in that park.)

Dame unos caramelos. (Give me some sweets.)

Unos caballeros preguntan por ti. (A few gentlemen are asking for you.)

Necesito unos pañuelos. (I need a few tissues.)

Unas (Some/A few)

Lastly, we have the article unas to refer to nouns that are feminine and plural. Here you have some examples with the Spanish indefinite article unas:

He encontrado unas monedas en el suelo. (I have found a few coins on the floor.)

Unas chicas me ayudaron. (Some girls helped me.)

Hay unas casas muy grandes en esta calle. (There are some very big houses on this street.)

Dime unas palabras en inglés. (Tell me some words in English.)

Let’s Agree! How to Construct a Sentence with Indefinite Articles

I am sure you have already heard about grammatical agreement. Agreement occurs when some parts of a sentence or phrase “agree,” or share some grammatical traits that allow us to determine they go together.

When constructing a sentence with indefinite articles, two important types of agreement are gender and number. This has to be your priority when choosing your articles, your nouns and even your adjectives. If you ignore grammatical agreement you will definitely sound like a lazy foreigner who does not even try. And you do not want that!

We will start with the noun. We will use the noun casa (house), which is feminine and singular.

Now we need to find an indefinite article that is also feminine and singular. Think about it, there is only an option… yes! Una is what we were looking for, and that gives us Una casa (a house).

We can now add an adjective. I love the color yellow, so our adjective will be amarillo. But, wait a second! We need a feminine, singular adjective so that it can agree with our noun and our article. We can follow the rules of gendered adjective endings and we get amarilla. That gives us Una casa amarilla (A yellow house).

Add a verb, an object or whatever you need to build a complete sentence, and the result may look like this:

Hay una casa amarilla cerca de la piscina. (There is a yellow house near the swimming pool.)

And that, ladies and gentlemen and gender-neutral friends, is how you create agreement in a sentence. Never forget!

The Exception to Article Agreement

However, there is one very small group of words that are an exception to the agreement rules stated above.

These rogue nouns have something in common: they are all feminine, singular and they all start with an accented “a” sound (a-, ha-).

The agreement rule specifically says that if a noun is feminine and singular, the indefinite article you have to use is una. But this group of words refuse to use una because they say they do not like so many “a” sounds together.

Instead, they use the indefinite pronoun un!


un águila veloz (a fast eagle)

un hacha pesada (a heavy ax)

un arma peligrosa (a dangerous weapon)

As you can clearly see, these nouns keep on being feminine, and the adjectives they accept can only be feminine.

Further, once you change the word into its plural form, the “revolution” ends and they adopt the feminine indefinite article once again. Have a look:

unas águilas veloces (some fast eagles)

unas hachas pesadas (some heavy axes)

unas armas peligrosas (some dangerous weapons)

Contexts that Require the Spanish Indefinite Article

Early in this post, we explained that indefinite articles are required when you are discussing something or someone that has yet to be specified or is not familiar to everyone you are talking to.

There are also some special contexts that always require an indefinite article in Spanish, which we will cover below.

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One in a Group

When talking about an unspecified person or object inside a group, we have to use the indefinite article. This happens simply because we are randomly picking up one item of the group as an example in order to represent all of the items in the group.

Here you have an example:

Un cocinero es una persona que cocina. (A cook is a person who cooks.)

We are not talking about a specific cook called Gordon who lives in Manhattan. We are talking about an unidentified cook who represents the whole group of cooks in the world.

Another example:

Un libro puede tener muchas páginas. (A book can have many pages.)

Once again, we are not talking about a specific book, but about any book. Our book is like a joker that represents all the books in existence.

Describing People or Things with Nouns

When describing people with a noun, the indefinite article is used. This is not because we do not know the person or the person is unspecified, but because we believe the person is one in a group of others like them.

Interestingly enough, the majority of times we will use a masculine noun (and the corresponding masculine article) even for describing women:

Eres un sol. (You are a sweetie. Literally, “You are a sun.” This can be applied to both men and woman and it does not need a change in gender).

Sois unos locos. (You are crazy people.)

We also have to use the indefinite article when we describe something or someone by using a noun plus an adjective.

Ana es una mujer muy guapa. (Ana is a very beautiful woman.)

Esta rosa es una flor delicada. (This rose is a delicate flower.)

El cáncer es una enfermedad muy peligrosa. (Cancer is a very dangerous disease.)

Single Units

Another situation when we use the indefinite article is actually identical both in Spanish and English, and that is when we are talking about a single unit (one) of something (or of somebody, as you will see in the examples).

It does not matter if you are talking about something known or unknown, specified or not, if you have only one of them, you have to use the indefinite article un/una.

He comprado tan solo un regalo. (I have only bought one present.)

Hay un niño en la cocina. (There is one child in the kitchen.)

Tengo una hermana. (I have one sister.)

Dime una palabra polaca. (Tell me one Polish word.)

Approximate Amounts

As we saw before, the Spanish indefinite article has two plural forms (unos, unas). With the meaning of “some/a few,” we are obviously going to use them when talking about approximate amounts of things or people.

Here you have some examples:

Necesito unas monedas. (I need some coins.)

Compra unas manzanas. (Buy a few apples.)

Tengo unos libros muy interesantes. (I have some very interesting books.)

Hay unos gatos en el tejado. (There are some cats on the roof.)

When to Omit the Indefinite Article

There are three situations when you should avoid using the indefinite article in Spanish:

Amounts That Might Be Zero

Let us examine the following two sentences:

Compra unas patatas. (Buy a few potatoes.)

¿Tiene patatas este estofado? (Does this stew contain potatoes?).

If you analyze both sentences, in the first one we are asking someone to buy some potatoes, or a few potatoes. We do not utter an exact number, but I think we can all agree some can mean something around five or 10 to 20.

In the second sentence we have not used the indefinite article. We are asking if the stew has any potatoes at all! We are not asking if the stew contains some 10 potatoes or some 25 potatoes, but whether the stew contains any potatoes altogether.

Occupations, Religions and Nationalities

As you may have inferred by the title of this sub-section, you should not use the Spanish indefinite article when talking about your occupation, your religion or your nationality.

Bear in mind English forces you to use the indefinite article when talking about your occupation. As for religion and nationality, Americans tend to omit the article, so we are safe here. Here you have some examples:

Soy profesor en la Universidad de Barcelona. (I am a professor at the University of Barcelona.)

Mi hermana es judía. (My sister is [a] Jew.)

Soy Americano. (I am [an] American.)

However, remember that if you have an adjective accompanying the occupation, religion or nationality, the indefinite article appears once again:

Es un gran profesor. (He is a great professor.)

Es un cristiano muy humilde. (He is a very humble Christian.)

John es un americano loco. (John is a crazy American.)

Medio, Otro, Cierto, Tal, Mil, Qué + Noun

Finally, there is a small group of words that, by nature, do not accept the indefinite article.

When you translate these words into English, most of them have the indefinite article around. This is simply the way they are said in English.

Medio (half): Necesito media hora para terminar. (I need half an hour to finish.)

Otro (another): Dame otra oportunidad. (Give me another chance.)

Cierto (one): Cierto día me dijo la verdad. (One day she told me the truth.)

Tal (such): Hay tal ruido que no puedo concentrarme. (There’s such a noise I can’t concentrate.)

Mil (thousand): Ayer me gasté mil dólares. (I spent a thousand dollars yesterday.)

Qué (what): ¡Que libro tan caro! (What an expensive book!)


So there you have it. All the information you need to know about the Spanish indefinite articles. Easy, right?

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