婴儿 (yīng ér) means 'infant'—a very young child, typically under one year old. The character 婴 (yīng) originally depicted a baby wrapped in swaddling clothes and carries the core meaning of 'infancy' or 'newborn'; 儿 (ér) means 'child' and functions here as a noun suffix that softens and specifies the meaning, forming a compound noun. Together, they emphasize the earliest stage of human childhood, distinct from 幼儿 (yòu ér, 'toddler') or 孩子 (hái zi, 'child' more generally).

This term is used in medical, developmental, and caregiving contexts—such as pediatric care, parenting guides, or public health announcements. It’s neutral and formal, commonly appearing in official documents, hospitals, and baby product labeling. Unlike colloquial terms like 小宝宝 (xiǎo bǎo bǎo), 婴儿 carries no diminutive or affectionate connotation; it’s precise, clinical, and respectful.