In what cases are “de” and “para” interchangeable?

Question

For example in these cases "de" and "para" seem to be interchangeable:

muebles de oficina / muebles para oficina

juguetes de niños / juguetes para niños

Are there any other cases where "de" and "para" can be used in the same manner?

Answer 1

According to Wiktionary, "de" has three uses:

1. A possessive indicator
2. To mean from (or from which)
3. An attributive noun linker.

In the first two meanings, "para" (which means "for") is incompatible with "de."

Example as possessive:

○   "el carro de Juan" => "John's car" (A more literal reading might be the car of John)

X   "el carro para Juan" => "the car for John"

Example as "from":

• from (in terms of location)

  • ○   "Yo soy de Texas." => "I am from Texas."

  • X   "Yo soy para Texas" => "I am for Texas" (This sounds weird, but might make sense in some situations.)

• from (in terms of which something proceeds out of)
  • ○    "una camisa de algodon" => "a shirt (made out) of cotton"
  • X   "una camisa para algodon" => "a shirt for cotton"

Now, in the third case the two can be interchanged loosely, and in most cases, the one that you choose to use is based solely upon convention. That said, there is a distinction between the two that should be noted, and in some cases using one or the other will result in a change of meaning. Considering one of your examples:

A) "muebles de (la) oficina" => "office furniture" or "furniture of the office"

B) "muebles para (la) oficina" => "furniture for the office"

In A, the furniture sounds like it is specifically designed for the office, and that it will remain like this (at least) for a while. In contrast, B doesn't carry this nuance as strongly. It could be any furniture (like a dinner table) that just happens to have been decided to be used in an office setting. Again, not a big difference, but when clarity or emphasis is needed in these types of cases, "de" would be preferred over "para".

Hope this helps :)

Answer 2

RAE shows this:

prep. para. Gorro de dormir. Ropa de deporte.

As the 25th definition of "de", so in this case "de" and "para" are both interchangeable in cases where you want to indicate ownership or affiliation.