Backward compatibility

property of a system, product, or technology that allows for interoperability with an older legacy system, or with input designed for such a system, especially in telecommunications and computing

thumb|A Phabricator task deprecating the Education extension for [[MediaWiki]] Deprecation is the discouragement of use of something human-made, such as a linguistic term, a proper name, a feature, design, functionality, piece of code, or practice. Typically a thing previously used is deprecated because it is—or is claimed or thought to be—inferior compared to other options now available. Deprecation is thus a mechanism for future improvement. Deprecation implies that the community (generally, or a community of experts, or a professional body governing a sector or industry) has determined that

design characteristic that allows a system to accept input intended for a later version of itself

cryptographic attack that forces the use of weaker or no encryption

Wikimedia list article

property where a computer system can run code compiled for another system unmodified