What, exactly does retro mean, and where does it come from? This post discusses the definition and derivation of this modern-looking but old-fashioned term.
The adjective retro stems, by way of the French term rétro (short for rétrograde), directly from a Latin preposition meaning “backward” or “behind” and pertains as a stand-alone word to a nostalgic or old-fashioned trend, especially in regard to apparel or decor. (Both those words, by the way, also come from Latin by way of French—Anglo-French, that is, in the case of the former term.)
Retrograde, itself, borrowed into English as such, not only can be identical in meaning with retro but also pertains more literally to backwardness: It refers to backward motion, occurrence, or performance or such behavior that is the opposite of the usual action, especially in astronomical contexts, in which it usually alludes to the apparent backward movement of planets. (The antonym is anterograde.) It is also synonymous with inverse and alludes to reversion to a simpler, inferior, or previous state. In medicine, it pertains to amnesia that affects memories from before a precipitating event such as an injury.
Retro appears as a prefix in a number of other words, including, most commonly, retroactive, which means “effective from a particular date in the past,” and retrospective, which can be synonymous with retroactive but also means “pertaining to the past or something that happened in the past. The word can also be used as a noun, usually to describe an exhibition of an artist’s previous works. Other noun forms are retrospect (literally, “looking back”), generally used in the phrase “in retrospect” (although the word is also used as an adjective and a verb), and retrospection, which describes the action of looking back.
Another familiar term is retrofit, a verb meaning “provide with new components not originally available” but usually pertaining to fortifying a structure against earthquake damage. Retrovirus, meanwhile, refers to a virus with an enzyme that reverses the usual genetic pattern. Finally, a retronym is a phrase coined in response to introduction of a variation of a well-known phenomenon that equals or supersedes the original in popularity or ubiquity, as when the adjective analog was appended to clock to describe a nondigital timepiece or when M&Ms were distinguished as “plain” or “peanut” when the latter type was introduced.
Numerous other terms, usually seen in medical or scientific contexts, also include the prefix.