"The boy's suit is new."
Translation:Le costume du garçon est nouveau.
Actually that is the usual case.
In English we would say "possession of owner", which is the format the French uses, too. However at some point in time somebody invented apostrophe s, and thus the format "owner's possession" was born.
In short, instead of saying "The boy's suit is new", we are really saying "The suit of the boy is new". Because the apostrophe is not used for possessives in French - we don't say "Le garcon's costume est nouveau".
- Garçon doesn't start with a vowel, so it would be le garçon.
- French doesn't have a genitive construction like "Le garçon's costume" to express possession. It has to be done (in this case) with de + article. https://www.thoughtco.com/french-possession-1368906
Original sentence (without contraction): Le costume de le garçon est nouveau. Translated word for word to english: The suit of the boy is new.
Contractions are mostly always needed in French with exception of some special cases. In this case, de and le contracts into du.
Final sentence (with contraction): Le costume du garçon est nouveau.
Contractions for de and indefinite articles "le", "la", and "les" are:
de+le= du ; de+la = de la (stays the same) ; de+les = des
I don't understand de vs du in this situation either. Also strange how there's no actual text in the lesson overview covering this section that I could refer to. I thought du is used in situations where quantity is unknown, we know it's one suit.
Although costume in French can mean both suit and costume in English, you can use another French word, déguisement to successfully distinguish between the two. le déguisement translates rougly to disguise (noun) in English, but can also mean costume as well.
(1Fr)Jenna, j'adore ton déguisement.
(1En)Jenna, I love your costume.
(2Fr)Détective, ce n'est pas juste un déguisement de squelette.
(2En)Detective, this isn't just a skeleton costume.
(3Fr)Le suspect porte un déguisement de Gorille.
(3En)Suspect is wearing a gorilla costume.
As always it also comes down context if you are distinguishing between suit and costume for the French word costume, but that can be easily accomplished.