nodule vs geode

nodule and geode both are nouns.

Word	Noun	Adjective	Verb	Adverb
nodule	Yes	No	No	No
geode	Yes	No	No	No

As nouns, geode is a hyponym of nodule; that is, geode is a word with a more specific, narrower meaning than nodule:

nodule: (mineralogy) a small rounded lump of mineral substance (usually harder than the surrounding rock or sediment)
geode: (mineralogy) a hollow rock or nodule with the cavity usually lined with crystals

nodule (noun)	geode (noun)
a small node	(mineralogy) a hollow rock or nodule with the cavity usually lined with crystals
(mineralogy) a small rounded lump of mineral substance (usually harder than the surrounding rock or sediment)
small rounded wartlike protuberance on a plant