an ovum

an egg, including fish roe / the beginning or start of something (compare the uses of English terms kernel and seed) / a beginner or rookie at something

one day

a tree kangaroo

embryology (of humans)

one, 1 / the first in order, foremost / the beginning / the best / a kind of; one of something / (card games) an ace / unity / the bottom string of a shamisen or other Japanese musical instrument

each person

special festival held annually at a shrine, usually related to the shrine's history

example, model case

isolated case