违反 (wéi fǎn) is a verb meaning 'to violate' or 'to contravene'—typically referring to breaking a rule, law, regulation, agreement, or principle. The character 违 (wéi) means 'to go against' or 'to disobey', while 反 (fǎn) reinforces this sense with meanings like 'to oppose' or 'to reverse'. Together, they form a compound that emphasizes deliberate noncompliance with an established standard or expectation.

This word is commonly used in formal, official, or serious contexts—such as legal documents, workplace policies, medical guidelines, or public health directives. It carries a negative connotation and implies accountability; saying someone 违反 a rule suggests they have knowingly or negligently breached it. It's often followed by the object of violation (e.g., 法律, 规定, 协议, 医嘱), and usually appears in written or semi-formal spoken Chinese rather than casual conversation.