"Nous avons un miroir."
Translation:We have a mirror.
Another sentence translated "Nous tournons notre chaise" to "We turn our chairs". Why is this one only singular?
This whole thing is about common sense and probabilities.
Two or more people can share one mirror:
- nous avons un miroir = we have a/one mirror
Two or more people may not share one chair.
- nous tournons notre chaise (= one each) / nos chaises (several chairs for several people) = we are turning our chairs (= several chairs for several people).