According to another post by Sitesurf du poil and des poils are interchangable, but I don't understand why.
Cheveu/cheveux is hair that grows from the human scalp. Poil/poils is hair that grows anywhere else.
As others have said, cheveux is hair on your head. Hair anywhere else on the body is "le poil / les poils". Also "le poil" is a coat on an animal - "Le chat a un poil marron." The cat has a brown coat.
The correct translation includes the possesive adjective, even though it's not in the French sentence. :/
If you're talking about "la poitrine" vs "sa poitrine", I think it's because in French you usually don't use possessive for body parts if it's obvious who the body part belongs to. In this case, it's obvious we're talking about the man's chest, so we don't have to specify it's his. That's why the English translation would be "his chest", even though it looks like "the chest".
But it would be also obvious we are talking about man's chest if the correct translation had "the" instead of "his".
This man has hair on the chest.
...does not sound natural in English. If I heard someone say that I would assume they were not a native English speaker.
Sometimes the literal translation is not the best translation. This is one of those times.
That would have to be "has" (because "man" is singular) but I don't know if that would be accepted, because it's not really what the French says.
How can you tell which consonants are sounded and which aren’t? Repetion? I regularly pronounce the l at the end of poil but usually consonants at the end of a word aren’t sounded.
A good tip that I heard on a Michel Thomas course described a rule for this as the 'CareFuL' rule. Generally if a word ends in C, F or L the consonant is sounded (except for 'c' if f it ends with 'nc' in which case the c is silent e.g. blanc).
To me "has hair on his chest" has exactly the same meaning as "has a hairy chest" and in English we would say the latter