"I remember the boy."
Translation:Je me souviens du garçon.
The verb 'se souvenir' is always followed by the preposition de, which contracts with definite articles: Je me souviens du (de+le) garçon
Remember that the partitive article "du" is used with uncountable nouns to mean "an unknown amount of a mass", which cannot suit this sentence.
Whenever "de" is followed by "le", there is a contraction to "du", and this works with possessives and all verbs constructed with the preposition "de":
- c'est le chien du (de+le) garçon = this is the boy's dog (lit. the dog of the boy)
- je parle du (de+le) garçon = I am talking of/about the boy