necklace vs neckband

necklace and neckband both are nouns.

Word	Noun	Adjective	Verb	Adverb
necklace	Yes	No	No	No
neckband	Yes	No	No	No

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

necklace: jewelry consisting of a cord or chain (often bearing gems) worn about the neck as an ornament (especially by women)
neckband: necklace that fits tightly around a woman's neck

Other hyponyms of necklace include chain, strand, string, chain, choker, collar, dog collar.

necklace (noun)	neckband (noun)
jewelry consisting of a cord or chain (often bearing gems) worn about the neck as an ornament (especially by women)	a band that fits around the neck and is usually folded over
	necklace that fits tightly around a woman's neck
	a band around the collar of a garment