You've already seen au and aux in our prepositions lesson, à fusing with le/les. The preposition de does the exact same thing, producing du and des.
1. The two contractions
| à + le → au | au marché |
| à + les → aux | aux toilettes |
| de + le → du | du marché |
| de + les → des | des toilettes |
2. À la, à l', de la, de l' never contract
Only the masculine singular (le) and the plural (les) fuse. The feminine singular and anything before a vowel sound stay as two separate words.
| de la plage | of/from the beach (no contraction) |
| de l'école | of/from the school (no contraction) |
3. Contracted de: possession and fixed expressions
French has no apostrophe-s, "the teacher's book" becomes "the book of the teacher," using de + article. The same contraction shows up after expressions that require de, like avoir besoin de, à côté de, près de, la fin de.
| le livre du professeur | the teacher's book |
| la voiture des voisins | the neighbors' car |
| Il a besoin du dictionnaire. | He needs the dictionary. |
| à côté du magasin | next to the store |
4. Watch out: this isn't the partitive du/des
Same spelling, different job: du and des also exist as partitive articles meaning "some." Only context tells them apart. Je bois du café. (I'm drinking some coffee, partitive.) vs. Je parle du café. (I'm talking about the café, contraction of de + le café.)
5. Quick reference
| du | de + le, of/about the (masc.) |
| des | de + les, of/about the (plural) |
| de la / de l' | no contraction (fem. / vowel sound) |