sword vs backsword

sword and backsword both are nouns.

Word	Noun	Adjective	Verb	Adverb
sword	Yes	No	No	No
backsword	Yes	No	No	No

As nouns, backsword is a hyponym of sword; that is, backsword is a word with a more specific, narrower meaning than sword:

sword: a cutting or thrusting weapon that has a long metal blade and a hilt with a hand guard
backsword: a sword with only one cutting edge

Other hyponyms of sword include broadsword, cavalry sword, saber, sabre, cutlas, cutlass, falchion, fencing sword, rapier, tuck.

sword (noun)	backsword (noun)
a cutting or thrusting weapon that has a long metal blade and a hilt with a hand guard	a sword with only one cutting edge
	a stick used instead of a sword for fencing