notochord vs rachis

notochord and rachis both are nouns.

Word	Noun	Adjective	Verb	Adverb
notochord	Yes	No	No	No
rachis	Yes	No	No	No

As nouns, rachis is a hypernym of notochord; that is, rachis is a word with a broader meaning than notochord:

notochord: a flexible rodlike structure that forms the supporting axis of the body in the lowest chordates and lowest vertebrates and in embryos of higher vertebrates
rachis: the series of vertebrae forming the axis of the skeleton and protecting the spinal cord

Other hypernyms of notochord include back, backbone, spinal column, spine, vertebral column.

notochord (noun)	rachis (noun)
a flexible rodlike structure that forms the supporting axis of the body in the lowest chordates and lowest vertebrates and in embryos of higher vertebrates	the series of vertebrae forming the axis of the skeleton and protecting the spinal cord
	axis of a compound leaf or compound inflorescence