‘双胞胎’ literally means ‘double embryo’ — ‘双’ (shuāng) means ‘two’ or ‘double’, ‘胞’ (bāo) refers to ‘womb’ or ‘embryo’ (often used in biological contexts related to conception and development), and ‘胎’ (tāi) means ‘fetus’ or ‘gestation’. Together, the term specifically denotes two babies born from the same pregnancy. It is a neutral, formal, and medically precise noun used in both everyday conversation and clinical settings.

The word applies to both identical (monozygotic) and fraternal (dizygotic) twins — it does not distinguish between them unless modified (e.g., 同卵双胞胎 for identical twins). Unlike English, Chinese doesn’t use ‘twins’ as an adjective, so you wouldn’t say *‘a twin baby’* — instead, you’d say ‘双胞胎之一’ (one of the twins) if needed. The term is commonly used when discussing family, pregnancy, childhood development, or medical care.