Definite and indefinite articles
English has 'the' and 'a'. Spanish has four versions of each, because the article also marks gender and number. The article tells you whether you mean a specific thing ('that one') or just any one ('some').
Definite articles (el, la, los, las)
el = the (masc. sing.): el gato. la = the (fem. sing.): la casa. los = the (masc. plural and mixed groups): los gatos. las = the (fem. plural): las casas. Use these when you mean a specific, known thing.
Indefinite articles (un, una, unos, unas)
un = a / one (masc.): un gato — a (some) cat. una = a / one (fem.): una casa — a house. unos = some (masc. plural): unos amigos — some friends. unas = some (fem. plural): unas amigas. Use these when introducing something for the first time, or when the specific identity doesn't matter.
First mention → 'a', then 'the'
First time: un/una. After it's been introduced: el/la. Veo un gato. El gato es negro. = 'I see a cat. The cat is black.' Just like English 'a' → 'the'.
When to drop the article
Before a profession with no description: Soy médico — I'm a doctor (no un). With señor, señora when addressing them: ¡Hola, señor García!. With first names: Ana es mi amiga. But: el señor García es médico (when talking about him in third person).
