胎児・胎仔|たいじtaiji[1]atamadaka (head-high)

1. nounfetus; foetus; embryo; baby in the womb; unborn baby

• Synonym胚子はいしWrittenWritten/formal prose for an embryo; 「胎児」 is the fetus at a later stage of development.
• Related受精卵じゅせいらんNeutralA neutral term for a fertilized egg, the very first stage; 「胎児」 is a later stage of development.
• Related胎芽たいがWrittenIn written/formal prose, an early embryo whose organs are just starting to form; 「胎児」 is the growing child once organ differentiation is complete.
• Related胚はいWrittenA written single-character term for an embryo, also covering plant germs such as wheat germ; 「胎児」 is the unborn child in the mother's womb.
• Antonym成人せいじんWrittenWritten/formal prose for an adult; it stands at the opposite end of the developmental scale from 「胎児」.
• Antonym大人おとなCasualColloquial for a grown-up; it marks the opposite end of the growth scale from 「胎児」.

Use 「胎児」 for an unborn child in the womb after its organs have formed. Earlier stages: 「受精卵」 (fertilized egg), then 「胎芽」/「胚」 or 「胚子」 (embryo). For the opposite stage of life, 「成人」 is formal, 「大人」 colloquial.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. （発生学はっせいがく）胎生たいせいの動物どうぶつの母体ぼたいの中なかで、胚はいが器官きかん原基げんきの分化ぶんかが完了かんりょうしてから出産しゅっさんするまでの、成長せいちょう中ちゅうの子こ。