sulphur dioxide vs dioxide

sulphur dioxide and dioxide both are nouns.

Word	Noun	Adjective	Verb	Adverb
sulphur dioxide	Yes	No	No	No
dioxide	Yes	No	No	No

As nouns, dioxide is a hypernym of sulphur dioxide; that is, dioxide is a word with a broader meaning than sulphur dioxide:

sulphur dioxide: a colorless toxic gas (SO2) that occurs in the gases from volcanoes; used in many manufacturing processes and present in industrial emissions; causes acid rain
dioxide: an oxide containing two atoms of oxygen in the molecule

Other hypernyms of sulphur dioxide include pollutant, gas.

sulphur dioxide (noun)	dioxide (noun)
a colorless toxic gas (SO2) that occurs in the gases from volcanoes; used in many manufacturing processes and present in industrial emissions; causes acid rain	an oxide containing two atoms of oxygen in the molecule