The original Farmall became known by the retronym "Regular". Where the introduction of a double retronym makes the adjective factually incorrect. Wi-Fi 1 is an unofficial retronym for 802.11b. Wi-Fi 2 is an unofficial retronym for 802.11a. This is however to use the term as a retronym. A synthetic instrument is the opposite of the retronym natural instrument. This use of the term "prime lens" is an example of a retronym. The Series1 (retronym) was the original TiVo digital video recorder. The title is a retronym; the episodes were not originally identified individually. The series acquired the retronym of "Godzilla&colon; The Original Animated Series" for its DVD release. The term "snail-mail" is a retronym to distinguish it from the quicker email. The term rectal tenesmus is a retronym to distinguish defecation-related tenesmus from vesical tenesmus. The retronym "lensless Schmidt" has been given to this configuration. This retronym designation was placed to differentiate it from the Metro Rapid service. The retronym "upright bicycle" is used to distinguish the style from recumbent bicycles.