防止 means 'to prevent' or 'to guard against' — it expresses the action of taking measures in advance to stop something undesirable from happening. The character 防 (fáng) means 'to guard' or 'to defend', while 止 (zhǐ) means 'to stop' or 'to halt'; together, they form a compound verb emphasizing proactive intervention before a problem occurs. It is commonly used in formal and semi-formal contexts — especially in public announcements, health advisories, safety instructions, and policy documents.

This verb typically takes a noun or clause as its object (e.g., 防止事故, 防止疾病传播), and often appears with modal verbs like 要, 应该, or 必须 to indicate necessity. It does not imply complete success — rather, it focuses on the effort or intention to avert an outcome. Unlike the more casual verb 避免 (to avoid), 防止 carries a stronger sense of vigilance and systematic precaution, making it frequent in medical, environmental, and regulatory discourse.