'Tóng shì' literally combines 'tóng' (same, together) and 'shì' (matter, affair, or work), suggesting people who share the same work or workplace. It refers specifically to people you work with in the same organization or department—regardless of rank, age, or role—and carries a neutral, respectful tone. Unlike English 'coworker', which can feel informal, 'tóng shì' is standard in both spoken and written Chinese across professional settings.

The term emphasizes shared professional context rather than personal closeness; it’s not used for classmates, friends, or family members who happen to work nearby. It’s commonly heard in office conversations, emails, introductions ('This is my colleague, Li Wei'), and formal documents. While 'tóng shì' can include supervisors and subordinates, more specific terms like 'shàng sī' (superior) or 'xià shǔ' (subordinate) are used when hierarchy matters.