sweet melon vine vs melon vine

sweet melon vine and melon vine both are nouns.

Word	Noun	Adjective	Verb	Adverb
sweet melon vine	Yes	No	No	No
melon vine	Yes	No	No	No

As nouns, melon vine is a hypernym of sweet melon vine; that is, melon vine is a word with a broader meaning than sweet melon vine:

sweet melon vine: any of several varieties of vine whose fruit has a netted rind and edible flesh and a musky smell
melon vine: any of various fruit of cucurbitaceous vines including: muskmelons, watermelons, cantaloupes, cucumbers

Other hypernyms of sweet melon vine include melon.

sweet melon vine (noun)	melon vine (noun)
any of several varieties of vine whose fruit has a netted rind and edible flesh and a musky smell	any of various fruit of cucurbitaceous vines including: muskmelons, watermelons, cantaloupes, cucumbers