file name vs filename

file name and filename both are nouns.

Word	Noun	Adjective	Verb	Adverb
file name	Yes	No	No	No
filename	Yes	No	No	No

As nouns, file name and filename are synonyms defined as:

file name and filename: (computer science) the name given to a computer file in order to distinguish it from other files; may contain an extension that indicates the type of file

Other synonyms of file name include computer file name, computer filename.

file name (noun)	filename (noun)
(computer science) the name given to a computer file in order to distinguish it from other files; may contain an extension that indicates the type of file	(computer science) the name given to a computer file in order to distinguish it from other files; may contain an extension that indicates the type of file