wivern vs wyvern

wivern and wyvern both are nouns.

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

As nouns, wivern and wyvern are synonyms defined as:

wivern and wyvern: 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

wivern (noun)	wyvern (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