downward compatible; backward compatible; compatible with input or components intended for lower tier or older systems, versions, etc.; upward compatible; forward compatible; compatible with input or components intended for higher tier or later systems, versions, etc.
upward compatible; forward compatible; compatible with input or components intended for higher tier or later systems, versions, etc.; downward compatible; backward compatible; compatible with input or components intended for lower tier or older systems, versions, etc.
backward compatible; downward compatible
forward compatible; upward compatible
binary level compatibility
compatibility test; interoperability test