Prepositional modifies, which describe things, adhere to the following rules:
A preposition + a noun modifying another noun is equivalent to an adjective:
The preposition à + noun is used to express the use, function, or characteristic of an object or person:
The preposition à + verb may be used to describe the purpose of a noun:
- une machine à écrire (a typewriter)
The preposition de + noun (and less frequently, en + noun) expresses the source or the content of an object:
The de + noun combination also expresses possession:
- C'est l'ami d'Anne. (It's Anne's friend.)
A preposition + a noun modifying a verb is equivalent to an adverb:
- Ils travaillent avec soin. (They work carefully.)