CO2 vs carbon dioxide

CO2 and carbon dioxide both are nouns.

Word	Noun	Adjective	Verb	Adverb
CO2	Yes	No	No	No
carbon dioxide	Yes	No	No	No

As nouns, CO2 and carbon dioxide are synonyms defined as:

CO2 and carbon dioxide: a heavy odorless colorless gas formed during respiration and by the decomposition of organic substances; absorbed from the air by plants in photosynthesis

Other synonyms of CO2 include carbonic acid gas.

CO2 (noun)	carbon dioxide (noun)
a heavy odorless colorless gas formed during respiration and by the decomposition of organic substances; absorbed from the air by plants in photosynthesis	a heavy odorless colorless gas formed during respiration and by the decomposition of organic substances; absorbed from the air by plants in photosynthesis