level crossing vs grade crossing

level crossing and grade crossing both are nouns.

Word	Noun	Adjective	Verb	Adverb
level crossing	Yes	No	No	No
grade crossing	Yes	No	No	No

As nouns, level crossing and grade crossing are synonyms defined as:

level crossing and grade crossing: intersection of a railway and a road on the same level; barriers close road when trains pass

level crossing (noun)	grade crossing (noun)
intersection of a railway and a road on the same level; barriers close road when trains pass	intersection of a railway and a road on the same level; barriers close road when trains pass