• Compliance is the fulfillment of specified requirements. (ISO 2394)
• Conformance is the fulfillment of specified requirements. (ISO 19105)
• Conformity is the fulfillment of a requirement. (ISO 22301)

Literally, compliance and conformance are identical. However, some consider compliance as forced adherence to specified requirements but conformance as voluntary adherence. Conformity is a related concept that emphasizes the fulfillment of a “single” requirement.