事故 (shì gù) is a compound noun meaning 'accident' or 'incident', typically referring to an unexpected, often harmful event—especially one involving injury, damage, or disruption. The first character, 事 (shì), means 'matter' or 'event'; the second, 故 (gù), means 'reason', 'cause', or 'past occurrence'. Together, they convey the idea of an unforeseen event with serious consequences—commonly used in contexts like traffic, workplace safety, or public health.

This word carries a formal or official tone and appears frequently in news reports, safety announcements, and official documents. It implies responsibility, investigation, or prevention—not casual mishaps (e.g., dropping your phone). While it can refer to minor incidents, its default connotation is negative and consequential: car crashes, factory malfunctions, medical errors, or natural disaster impacts. It’s rarely used for trivial or humorous situations, unlike English 'incident' which can be neutral.