24 bit
The term "24 bit" is used in the discussion of digital technology to describe a digital word with a wordlength of 24 bits.
In digital audio, 24 bit can be the wordlength of the digital audio information and is directly related to its resolution in the amplitude domain or the signal-to-noise ratio. The signal-to-noise ratio can also be expressed in dB as the dynamic range and as the names imply; describe the range between the quietest possible signal and the loudest possible signal. With a theoretical limit of nearly 144dB dynamic range; digital audio converters with 24 bit resolution can accurately encode high quality analog audio. So even though computer technology routinely operates with 32 bit wordlength and can calculate with 64 bit precision; it is unlikely that the 24 bit audio standard is likely to change in the foreseeable future.
Most professional audio engineers and other "Golden Ears" agree that 24 bit encoding is necessary to capture the full resolution of high quality analog audio.