sugar beet vs common beet

sugar beet and common beet both are nouns.

Word	Noun	Adjective	Verb	Adverb
sugar beet	Yes	No	No	No
common beet	Yes	No	No	No

As nouns, common beet is a hypernym of sugar beet; that is, common beet is a word with a broader meaning than sugar beet:

sugar beet: form of the common beet having a sweet white root from which sugar is obtained
common beet: biennial Eurasian plant usually having a swollen edible root; widely cultivated as a food crop

Other hypernyms of sugar beet include beet, Beta vulgaris.

sugar beet (noun)	common beet (noun)
white-rooted beet grown as a source of sugar	biennial Eurasian plant usually having a swollen edible root; widely cultivated as a food crop
form of the common beet having a sweet white root from which sugar is obtained