胎児（たいじ、taiji）
- fetus

The Japanese word 胎児 (たいじ - taiji) refers to an unborn baby, or fetus, from the embryonic period until birth. It encompasses the stage of development within the mother's womb. 胎児 represents the developing human before it is born.

⚫︎胎児の発育を観察する。 Translation: To observe the development of the fetus. ⚫︎ 妊娠中の女性は、健康な胎児のために適切な食事を摂る必要がある。 Translation: Pregnant women need to eat a proper diet for a healthy fetus. ⚫︎ 胎児は母親の子宮内で成長する。 Translation: The fetus grows inside the mother's womb.

This word is used in a medical, scientific, or formal context. It's common in discussions about pregnancy, prenatal care, medical research, and biology. You'd use it when talking about the unborn baby's development, health, or potential issues. It is not typically used for informal discussions about "babies".

⚫︎The word is most commonly written using the kanji 胎児. ⚫︎ The reading is たいじ (taiji) in hiragana. ⚫︎ There are no other common ways to write this word. ⚫︎ The okurigana is fixed.

There aren't direct synonyms in Japanese. Related terms that might be used in some contexts include: ⚫︎ 胎内（たいない - tainai） - "inside the womb" (more a location than a synonym) ⚫︎ お腹の赤ちゃん（おなかのあかちゃん - onaka no akachan） - "baby in the belly" (more casual)

⚫︎ 新生児（しんせいじ - shinseiji） - newborn baby ⚫︎ 乳児（にゅうじ - nyuuji） - infant

医師は、超音波検査で《胎児の心拍を確認した。》 ・Translation: The doctor confirmed the fetus's heartbeat with an ultrasound. ・Explanation: This sentence describes a common medical procedure to monitor the unborn baby.

その薬は、《胎児に悪影響を及ぼす可能性がある。》 ・Translation: That medicine may have a negative effect on the fetus. ・Explanation: This sentence highlights the importance of protecting the unborn baby from harmful substances.

The word 胎児 is a combination of two kanji: ⚫︎ 胎 (たい - tai) - womb, uterus, or the state of being pregnant ⚫︎ 児 (じ - ji) - child Therefore, 胎児 literally means "womb child" or "child in the womb."