whip-scorpion vs arachnid

whip-scorpion and arachnid both are nouns.

Word	Noun	Adjective	Verb	Adverb
whip-scorpion	Yes	No	No	No
arachnid	Yes	No	No	No

As nouns, arachnid is a hypernym of whip-scorpion; that is, arachnid is a word with a broader meaning than whip-scorpion:

whip-scorpion: nonvenomous arachnid that resembles a scorpion and that has a long thin tail without a stinger
arachnid: air-breathing arthropods characterized by simple eyes and four pairs of legs

Other hypernyms of whip-scorpion include arachnoid.

whip-scorpion (noun)	arachnid (noun)
nonvenomous arachnid that resembles a scorpion and that has a long thin tail without a stinger	air-breathing arthropods characterized by simple eyes and four pairs of legs