“An elderly woman was the victim of a street robbery which netted the thief just £10. … The offender walked behind the victim for a short time before grabbing her handbag, causing her to fall to the floor.” (My local paper this week)
In this context, I should have written ground rather than floor, as the event took place outside. The Oxford Reference Dictionary gives, as section 7 under floor, “colloq. ground”, but the usual formal meaning of ‘floor’ is a surface under cover, and ‘ground’ is a surface covered only by the sky.
This wording explains why ‘floor’ can also be the surface of a forest, cave or ocean, all of which have a covering that is not directly the sky.
Interestingly, although I can accept either ‘cave floor’ or ‘floor of the cave’, and ‘sea/ocean floor’ or (less easily) ‘floor of the sea/ocean’, for ‘forest floor’ I can’t accept the alternative ‘floor of the forest’. And although wood is more-or-less synonymous with forest, I can’t accept ‘*wood floor’ at all.
Do others agree? or is this simply a part of my idiolect?