lying under oath vs perjury

lying under oath and perjury both are nouns.

Word	Noun	Adjective	Verb	Adverb
lying under oath	Yes	No	No	No
perjury	Yes	No	No	No

As nouns, lying under oath and perjury are synonyms defined as:

lying under oath and perjury: criminal offense of making false statements under oath

Other synonyms of lying under oath include bearing false witness.

lying under oath (noun)	perjury (noun)
criminal offense of making false statements under oath	criminal offense of making false statements under oath