[co_dh]

Human makes a lot of inconsistent thing: We usually think the 1st floor, and the basement as 1st underground floor ( -1), but the floor jumps from 1 to -1!

Also, the time jump from 11AM to 12PM to 1PM! So I think more human friendly sometimes means more confusing.

[BorisTheBrave]

In Europe, the floor level with the ground is called "ground" or "0".

[luispauloml]

That's true. But as for floor numbering, specifically, it depends on the country: some places have a "ground floor" between the 1st underground floor and the 1st "above ground" floor.

[copperx]

It's like English pronunciation, there's little logic. I gave up finding logic in these things at an early age, and resorted to memorizing everything instead.