finger's breadth vs fingerbreadth

finger's breadth and fingerbreadth both are nouns.

Word	Noun	Adjective	Verb	Adverb
finger's breadth	Yes	No	No	No
fingerbreadth	Yes	No	No	No

As nouns, finger's breadth and fingerbreadth are synonyms defined as:

finger's breadth and fingerbreadth: the length of breadth of a finger used as a linear measure

Other synonyms of finger's breadth include digit, finger.

finger's breadth (noun)	fingerbreadth (noun)
the length of breadth of a finger used as a linear measure	the length of breadth of a finger used as a linear measure