Spanish nouns are often accompanied by a definite article or an indefinite article. A lot of the time, the inclusion or omission of an indefinite article in Spanish matches up with the English translation.
Tengo una manzana.
I have an apple.
¿Hay manzana en esta ensalada?
Does this salad have apple(s)?
However, there are also times that you will use the indefinite article in Spanish but not in the English translation. Below you will find a some helpful guidelines for remembering when and when not to use the indefinite article in Spanish.
When to Use the Indefinite Article
2. To Say There is Exactly One of Something
Quiero una manzana.
I want an apple.
Tengo un libro de gramática.
I have a grammar book.
2. To Describe a Person Using a Noun
Mi hermano es un genio.
My brother is a genius.
Mis padres son unos héroes.
My parents are heroes.
3. To Describe an Approximate Amount of Something
Tengo unos cincuenta dólares.
I have about fifty dollars.
Compró unos perros calientes.
He bought a few hot dogs.
Necesitamos unas guitarras.
We need a few guitars.
When Not to Use the Indefinite Article
1. To Describe an Unknown Amount of Something
¿Hay calabaza en la sopa?
Is there a (any) squash in the soup?
¿Hay arañas en su sótano?
Are there spiders in your basement?
2. To Talk about Professions, Religion, or Nationality
Soy profesora de español.
I am a Spanish professor.
Él es católico.
He is a Catholic.
Mis amigos son peruanos.
My friends are Peruvian.
If you modify a profession, religion, or nationality with an adjective, then you do use an indefinite article.
Soy una profesora de español muy buena.
I am a very good Spanish teacher.
Él es un católico muy creyente.
He is a very faithful Catholic.
Mis amigos son unos peruanos muy simpáticos.
My friends are very nice Peruvians.
To Talk about Possessions with Tener
¿Tienes coche?
Have you got a car?
Ahora tenemos tele.
Now we've got a TV
If you modify the possession with an adjective, then you do use an indefinite article.
Tengo un coche rojo.
I have a red car.
Ahora tenemos un teléfono inalámbrico.
Now we have a wireless phone.
3. When a Noun is Preceded by Cierto/a, Medio/a, Tal(es), Otro/a, or Mil
Cierta persona tiene un secreto.
A certain person has a secret.
Iremos al cine en media hora.
We'll go to the theater in a half hour.
No me cuentes tal cosa.
Don't tell me such a thing.
Dame otra camisa.
Give me another shirt.
Él ganó mil dólares.
He won a thousand dollars.
