'Xī yī' literally means 'Western medicine' — 'xī' (west) refers to Western countries, especially Europe and North America, while 'yī' means 'medicine' or 'medical practice'. Together, the term denotes the system of diagnosis and treatment based on modern scientific methods, including anatomy, pharmacology, clinical trials, and evidence-based protocols. It contrasts with traditional Chinese medicine (TCM), known as 'zhōng yī'.

This term is commonly used in healthcare discussions, hospital settings, and everyday conversations about treatment options. People may say they 'see a xī yī doctor' for an infection, choose 'xī yī treatment' for cancer, or compare 'xī yī' and 'zhōng yī' approaches to chronic conditions. While neutral in tone, it carries cultural weight — often implying scientific rigor, but sometimes sparking debate about holistic care versus symptom-focused intervention.