For an example, take the following two sentences: Tengo un viejo amigo. Tengo un amigo viejo. A "safe" translation of these two sentences would be fairly easy to come up with: "I have an old friend." But what does that mean? Does it mean that my friend is elderly? Or does it mean that the person has been a friend for a long time?
It may surprise you to find out that in Spanish the sentences aren't so ambiguous, for viejo can be understood differently depending on where it is in relation to the noun that is described. Word order does make a difference. In this case, tengo un viejo amigo typically means "I have a longtime friend," and tengo un amigo viejo typically means "I have an elderly friend." Similarly, someone who has been a dentist for a long time is un viejo dentista, but a dentist who is old is un dentista viejo. Of course it is possible to be both — but in that case the word order will indicate what you're emphasizing.
Viejo is far from the only adjective that functions that way, although the distinctions aren't nearly always as strong as they are with viejo. Here are examples of some of the more common such adjectives. Context still matters, and there may be exceptions, but these are guidelines to pay attention to:
- antiguo: la antigua silla, the old-fashioned chair; la silla antigua, the antique chair
- grande: un gran hombre, a great man; un hombre grande, a big man
- mismo: el mismo atleta, the same athlete; el atleta mismo, the athlete himself
- nuevo: el nuevo libro, the brand-new book, the newly acquired book; el libro nuevo, the newly made book
- pobre: esa pobre mujer, that poor woman (in the sense of being pitiful); esa mujer pobre, that woman who is poor
- propio: mi propios zapatos, my own shoes; mis zapatos propios, my appropriate shoes
- solo: un solo hombre, only one man; un hombre solo, a lonely man
- triste: un triste viaje, a dreadful trip; un viaje triste, a sad trip
- único: la única estudiante, the only student; la estudiante única, the unique student
You may notice a pattern above: When placed after a noun, the adjective tends to add a somewhat objective meaning, while placed before it often provides an emotional or subjective meaning.
These meanings aren't always hard and fast and can depend to a certain extent on context. For example, antigua silla might also refer to a well-used chair or a chair with a long history. Some of the words also have other meanings; solo, for example, can also mean "alone." And in some cases, as with nuevo, placement can also be a matter of emphasis rather than simply of meaning. But this list does provide a guide that should be useful in helping determine the meaning of some double-meaning adjectives.