wyvern vs wivern

wyvern and wivern both are nouns.

Word	Noun	Adjective	Verb	Adverb
wyvern	Yes	No	No	No
wivern	Yes	No	No	No

As nouns, wyvern and wivern are synonyms defined as:

wyvern and wivern: a fire-breathing dragon used in medieval heraldry; had the head of a dragon and the tail of a snake and a body with wings and two legs

wyvern (noun)	wivern (noun)
a fire-breathing dragon used in medieval heraldry; had the head of a dragon and the tail of a snake and a body with wings and two legs	a fire-breathing dragon used in medieval heraldry; had the head of a dragon and the tail of a snake and a body with wings and two legs