The word hifi is a term used to refer to the high quality sound reproduction.

Ideally equipment Hi-Fi delivers minimum noise and distorsion.Il was created in 1973 by the German Institut fur Normung DIN Deutshe, the standart DIN 45500.C is and DIN 45500 succeed has set the standard high fidélité.La therefore gave the assurance that the equipment was able to give her a good quality reproduction. In theory only the stereo equipment that could meet the standard support the fi-term but in practice this term was largely a given audio products do not meet the basic specifications of DIN. In the 1990s, the word hifi will largely be replaced by the term "high-end audio" or high end audio to give "Audiophile" today.

Wikipedia