ovum vs ootid

ovum and ootid both are nouns.

Word	Noun	Adjective	Verb	Adverb
ovum	Yes	No	No	No
ootid	Yes	No	No	No

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

ovum: the female reproductive cell; the female gamete
ootid: mature ovum after penetration by sperm but before the formation of a zygote

Other hyponyms of ovum include egg, ovule.

ovum (noun)	ootid (noun)
the female reproductive cell; the female gamete	mature ovum after penetration by sperm but before the formation of a zygote