Definition - Articles are words mostly used before nouns. In Spanish, articles are the key to understand the gender of nouns because they are divided in two genders, just like nouns are. Examples of Spanish articles followed by nouns:
             • un hombre [a man], la mujer [the woman], ...

Types - There are two kinds of articles: definite and indefinite.

Definite articles are used to indicate specific nouns (e.g. the person of which we have already spoken in a speech, the thing about which we have already read in a written passage, etc.) The Spanish definite articles are:
             • Singular masculine - el libro [the book]
             • Singular feminine - la carta [the letter]
             • Plural masculine - los libros [the books]
             • Plural feminine - las cartas [the letters]

Indefinite articles refer to nouns in a non-specific way. The Spanish indefinite articles are:
             • Singular masculine - un museo [a museum]
             • Singular feminine - una calle [a street]
             • Plural masculine - unos museos [some museums]
             • Plural feminine - unas calles [some streets]

Note: the meaning of the plural form of the Spanish indefinite articles is rendered in English with expressions like 'a few', 'some', 'a couple of'.