Translation guide
In Japanese, the word for 'infant' depends on the child's age and the context. The most common general term is 赤ちゃん (akachan) for babies, while more formal or medical terms like 乳児 (nyūji) are used in specific situations.
To refer to a baby or very young child in everyday, warm contexts.
The most common and affectionate word for a baby. Used by everyone, from parents to strangers.
赤ちゃんが泣いている。
The baby is crying.
かわいい赤ちゃんだね。
What a cute baby!
Also means baby, slightly more colloquial or old-fashioned than 赤ちゃん. Often used in storytelling or casual speech.
赤ん坊がすやすや眠っている。
The baby is sleeping peacefully.
To refer to an infant in medical, official, or formal contexts, specifically a child under one year old.
Formal/medical term for an infant (under 1 year). Used in healthcare, legal documents, and statistics.
乳児の健康診断に行く。
I'm going for the infant's health check-up.
乳児死亡率は低下している。
The infant mortality rate is declining.
To refer to a newborn baby, especially in the first month of life.
Medical/formal term for a newborn (up to about 4 weeks). Used in hospitals and official records.
新生児は一日のほとんどを寝て過ごす。
Newborns spend most of the day sleeping.
A descriptive phrase meaning 'newborn baby', used in everyday conversation.
生まれたばかりの赤ちゃんはとても小さい。
A newborn baby is very small.
To refer to a child in the early stages of life, often still a baby or toddler.
Formal term for an infant or toddler (usually 1-6 years, but can include younger). Used in education and legal contexts.
幼児向けの絵本を買った。
I bought a picture book for infants/toddlers.
A general phrase meaning 'small child', often used for infants and toddlers in everyday speech.
小さな子供が公園で遊んでいる。
Small children are playing in the park.
赤ちゃん is the everyday word for a baby, used affectionately. 乳児 is a formal/medical term for an infant under 1 year. 新生児 specifically means a newborn (first 4 weeks). Use 赤ちゃん in casual conversation, and the others in official or medical contexts.
The English loanword インファント is not commonly used in Japanese. Stick to native Japanese terms.