precava vs superior vena cava

precava and superior vena cava both are nouns.

Word	Noun	Adjective	Verb	Adverb
precava	Yes	No	No	No
superior vena cava	Yes	No	No	No

As nouns, precava and superior vena cava are synonyms defined as:

precava and superior vena cava: receives blood from the head and arms and chest and empties into the right atrium of the heart; formed from the azygos and both brachiocephalic veins

precava (noun)	superior vena cava (noun)
receives blood from the head and arms and chest and empties into the right atrium of the heart; formed from the azygos and both brachiocephalic veins	receives blood from the head and arms and chest and empties into the right atrium of the heart; formed from the azygos and both brachiocephalic veins