egg cell vs ovule

egg cell and ovule both are nouns.

Word	Noun	Adjective	Verb	Adverb
egg cell	Yes	No	No	No
ovule	Yes	No	No	No

As nouns, ovule is a hyponym of egg cell; that is, ovule is a word with a more specific, narrower meaning than egg cell:

Other hyponyms of egg cell include egg, ootid.

egg cell (noun)	ovule (noun)
the female reproductive cell; the female gamete	a small or immature ovum
	a small body that contains the female germ cell of a plant; develops into a seed after fertilization