The indefinite articles in English are the words "a" or "an,"
and in the plural "some," "a few," or "several." Spanish also has
four words for this article: un, una, unos, and unas.
This section is closely related to the section on nouns, and the
two categories should be studied together for a complete view of
the subject.
Forms
Spanish has four forms of the indefinite article, corresponding
to the singular and plural of masculine and feminine nouns.
Singular –> Plural:
un (fusil) –> unos (fusiles)
una (batalla) –> unas (batallas)
Uses
The indefinite article translates the word "a" or "an," and in
the plural "some," "a few" or "several."
Tengo una cuenta corriente.(I have a bank
account.)
Me quedan unas monedas.(I have a few coins
left.)
The articles are used with the gender and number of their
corresponding nouns, with one exception. When feminine nouns begin
with a stresseda or ha in the singular they
take the masculine indefinite article.
un ala, unas alas(a wing, some wings)
un alba, unas albas(a dawn, some dawns)
un hambre, unas hambres(a hunger, some
hungers)
The article is not used after ser with unmodified
professions, occupations, nationalities, religions, etc.
Ellos son ingenieros.(They are engineers.)
Ellas son guatemaltecas.(They are
Guatemalan.)
Es católico.(He is a Catholic.)
But...
Es un buen católico.(He is a good
Catholic.)
It is omitted before the numbers cien, ciento, and
mil, before otro/a, medio/a and cierto/a, and
before tal (such a) and ¡qué...! (what
a...!)