The English word beautiful in French is 'belle' which is a feminine adjective.
The male equivalent of belle is 'beau' (also used in the English language to describe a boyfriend or male admirer)
It does get slightly confusing though because we would describe a handsome man as 'un bel homme' as beau is changed to bel in this case because of the unaspirated 'h' of homme.
Obviously the word beautiful can be used to describe objects as well as people, and as you know, in French inanimate objects have a male or female gender (I never could understand that) so when describing an object it is important to use the appropriate gender.
Therefore, because a house is feminine in French, to describe a pretty one you would say "une belle maison"
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