High fidelity or 'hi-fi' reproduction is a quality standard indicating that the reproduction of sound is very faithful to the original. High fidelity aims to achieve minimal or unnoticeable degrees of noise and distortion. The term 'high fidelity' tends to be applied to any reasonable-quality home music system.
High fidelity enthusiasts are often referred to as 'audiophiles'. As the term hi-fi is today used generically, the expensive end of the home audio electronics spectrum is often named as 'high end.'
The 1920s saw the introduction of electronic amplification, microphones, and the application of quantitative engineering principles to the reproduction of sound. Essential pioneering was done at Bell Laboratories and commercialised by Western Electric. Acoustically-recorded disc records with arbitrarily peaky frequency response were replaced by electrically-recorded records.
Meanwhile, the nascence of radio meant increased popularity for loudspeakers and tube amplifiers, so there was a period of time during when radio receivers commonly used loudspeakers and electronic amplifiers to reproduce sound, while phonographs were still commonly purely mechanical and acoustic. Later, electronic phonographs became available, as stand-alone units or designed to play through consumers' radios.
Modern hi-fi equipment usually includes input sources such as CD players and Digital Audio Broadcasting (DAB) tuners, an amplifier, and loudspeakers. Some modern hi-fi equipment can be connected digitally using fibre optic and TOSLINK cables and may have USB ports and WiFi connection capability.
One modern component that is making fast inroads in acceptance is the music server consisting of one or more hard drives that store music in the form of computer files such as FLACs. When the said music is stored in an audio file format that is lossless (such as FLAC or Monkey Audio ,the opposite of lossy file formats such as MP3), the computer playback of recorded audio can indeed serve as an audiophile-quality source for a hi-fi system.
If the hi-fi system includes components such as a projector, television, satellite decoder, DVD player, surround sound amplification and multi-channel loudspeakers, then it is often termed 'home cinema' or a 'home theatre system'.