pineal body vs ductless gland

pineal body and ductless gland both are nouns.

Word	Noun	Adjective	Verb	Adverb
pineal body	Yes	No	No	No
ductless gland	Yes	No	No	No

As nouns, ductless gland is a hypernym of pineal body; that is, ductless gland is a word with a broader meaning than pineal body:

pineal body: a small endocrine gland in the brain; situated beneath the back part of the corpus callosum; secretes melatonin
ductless gland: any of the glands of the endocrine system that secrete hormones directly into the bloodstream

Other hypernyms of pineal body include endocrine, endocrine gland.

pineal body (noun)	ductless gland (noun)
a small endocrine gland in the brain; situated beneath the back part of the corpus callosum; secretes melatonin	any of the glands of the endocrine system that secrete hormones directly into the bloodstream