First floor and Ground-floor

First floor noun - The floor of a building that is at or nearest to the level of the ground around the building.

Ground-floor and first floor are semantically related. In some cases you can replace phrase "Ground-floor" with "First floor", this phrases are similar.

Ground-floor adjective - On the floor closest to level with the ground.

First floor and ground-floor are semantically related. You can use "First floor" instead a noun phrase "Ground-floor".