From the German noun
Ersatz, meaning "substitute", comes the English adjective
ersatz, a rough synonym of
faux, insofar as both incorporate a suggestion of inferiority along with 'fakeness'. It means fake, especially if fake and inferior.
A relatively new word to English, ersatz's oldest recorded use in English literature, according to the Oxford English Dictionary, is in the 1875 edition of the Encyclopedia Britannica, used in reference to the German army. However, it is quite possible that the intended use there was as a proper noun; a name -- "the Ersatz reserve," (for those exempt from service). If this was the intention of the Britannica editors, it can't very well be said to have been used yet as an English word, and for the following 60-plus years, it was generally written capitalized, often in quotes, thereby marking it as 'not an English word,' and rather, as still a truly German word.
But in 1942, ersatz was used for the first time in published literature as a lower-case, bona fide English adjective, by L.B. Namier in his book, Conflicts, writing of "Hitler's jack-boots and ersatz uniforms." Thereafter, it became a bit more common, the quotes disappeared, and the word was soon regarded as genuine English.
Ersatz in English today retains an academic, esoteric air, and like the French-derived English word faux, few literary situations -- and still fewer conversational situations -- would legitimately call for its use over fake, which is far more common and much more widely understood.
Sources:
- ersatz. OED online.
- ersatz. Merriam-Webster Online, at http://www.m-w.com
- Personal experience