ground floor vs ground level

ground floor and ground level both are nouns.

Word	Noun	Adjective	Verb	Adverb
ground floor	Yes	No	No	No
ground level	Yes	No	No	No

As nouns, ground floor and ground level are synonyms defined as:

ground floor and ground level: the floor of a building that is at or nearest to the level of the ground around the building

Other synonyms of ground floor include first floor.

ground floor (noun)	ground level (noun)
the floor of a building that is at or nearest to the level of the ground around the building	the floor of a building that is at or nearest to the level of the ground around the building
becoming part of a venture at the beginning (regarded as position of advantage)	the height of the ground on which something stands