bis and ter
Sometimes you may see bis and ter as part of the name of a specification. They are usually used as a suffix to an existing name. These are equivalent to "version 2" and "version 3"; although, they are usually used to connote a correction to a specification where significant problems were discovered. So bis and ter usually do not add features, but may change protocols significantly to make them incompatible with the previous specification. This convention is often used in IETF and ITU-T/UIT-T specifications.
Examples: V.32bis for analog modems and DNSSEC-bis for DNS Security Extension.
To add to the confusion there was no V.32ter specification, but numerous manufacturers implemented non-standard extensions to V.32bis referred to as V.32terbo, where terbo (not turbo, but terbo) obviously makes you think of ter. Later there was a specification called V.34 (02/98) which corrected errors in the previous V.34 specification and was frequently called V.34bis even though this was not the official name for the corrected standard. The IEEE managed to set a worse record for bad naming conventions with just about every name they ever gave to an 802.11 wireless specification over a 20 year span. The WI-FI Alliance has recently attempted to help the confusion by coming up with new, simpler names. For example, 802.11ax is called WI-FI 6; although, 802.11ay has not been given a friendly name because it's just an improvement over 802.11ad and isn't meant to compete with application for what most consumers think of as WiFi... maybe.