乳幼児[nyuuyouji] infants
幼い[osanai] very young
幼馴染[osananajimi] childhood friend
幼魚[yougyo] fry (young fish)
幼形進化[youkeishinka] paedomorphosis

幼子[osanago] infant
幼児[youji] infant
幼児ポルノ[youjiporuno] child pornography
幼児語[youjigo] baby talk (like choo-choo for train, etc.)
幼時[youji] childhood

ランブル鞭毛虫[ranburubenmouchuu] giardia (flagellate protozoan)
ランブル鞭毛虫症[ranburubenmouchuushou] giardiasis
いも虫[imomushi] hornworm (caterpillar of a hawk moth)
益虫[ekichuu] useful insect
円虫類[enchuurui] round worms

夏虫[natsumushi] summer insect
蛔虫[kaichuu] roundworm (Ascaris lumbricoides)
害虫[gaichuu] harmful insect
鈎虫[kouchuu] hookworm
寄生虫[kiseichuu] parasite