overcup oak vs oak

overcup oak and oak both are nouns.

Word	Noun	Adjective	Verb	Adverb
overcup oak	Yes	No	No	No
oak	Yes	No	No	No

As nouns, oak is a hypernym of overcup oak; that is, oak is a word with a broader meaning than overcup oak:

overcup oak: medium-large deciduous timber tree of central and southern United States; acorns deeply immersed in the cup and mature in first year
oak: a deciduous tree of the genus Quercus; has acorns and lobed leaves

Other hypernyms of overcup oak include oak tree.

overcup oak (noun)	oak (noun)
medium-large deciduous timber tree of central and southern United States; acorns deeply immersed in the cup and mature in first year	a deciduous tree of the genus Quercus; has acorns and lobed leaves
	the hard durable wood of any oak; used especially for furniture and flooring