scorpion vs arachnoid

scorpion and arachnoid both are nouns.

Word	Noun	Adjective	Verb	Adverb
scorpion	Yes	No	No	No
arachnoid	Yes	Yes	No	No

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

scorpion: arachnid of warm dry regions having a long segmented tail ending in a venomous stinger
arachnoid: air-breathing arthropods characterized by simple eyes and four pairs of legs

Other hypernyms of scorpion include arachnid.

scorpion (noun)	arachnoid (noun)
arachnid of warm dry regions having a long segmented tail ending in a venomous stinger	air-breathing arthropods characterized by simple eyes and four pairs of legs
	the middle of the 3 meninges

scorpion (adjective)	arachnoid (adjective)
	relating to or resembling a member of the class Arachnida