"He wants breakfast."
Translation:उसे नाश्ता चाहिए।
What is the difference between ouse and vahe...and when do you know which to use?
Do you mean उसे and वह?
उसे is the dative form of वह and roughly means 'to him/her/it'.
To see whether you have to use उसे or वह (when उसे/वह is used as a pronoun he/she/it not as 'that), replace the pronoun in the sentence with a noun like पीटर. If there is no postposition after पीटर in the new sentence, you need to use वह. If पीटर is followed by the postposition को, replace पीटर को with उसे.
Eg: पीटर गाता है (Peter sings ) -- वह गाता है (He sings)
पीटर को किताब दो (Give the book to Peter) -- उसे किताब दो (Give the book to him)
पीटर को मेरा गाना पसंद है (Peter likes my song, literally: To Peter, this song is liked) --उसे मेरा गाना पसंद है (He likes my song, literally: To him, my song is liked) (more natural way of saying)
पीटर मेरे गाने को पसंद करता है (Peter likes my song) -- वह मेरे गाने को पसंद करता है (He likes my song) (also correct way of saying but used less)
पीटर को नाश्ता चाहिए (Peter wants breakfast, literally: To Peter, breakfast is needed) -- उसे नाश्ता चाहिए (He wants breakfast, literally: To him, breakfast is needed)
पीटर नाश्ता चाहता है (Peter wants breakfast) -- वह नाश्ता चाहता है (He wants breakfast) (also correct way of saying)
Thanks for this explanation. I really need to get my head round this one. Hopefully, it will all click in place. Tbh have not come across terms like 'dative' 'oblique' and 'post position...as taught English in very non classical way in the 70s!