n. A unit of memory or data equal to the amount used to represent one character; on modern architectures this is usually 8 bits, but may be 9 on 36-bit machines. Some older architectures used 'byte' for quantities of 6 or 7 bits, and the PDP-10 supported 'bytes' that were actually bitfields of 1 to 36 bits!
These usages are now obsolete, and even 9-bit bytes have become rare in the general trend toward power-of-2 word sizes.
Historical note: The term originated in 1956 during the early design phase for the IBM Stretch computer; originally it was described as 1 to 6 bits (typical I/O equipment of the period used 6-bit chunks of information).
The move to an 8-bit byte happened in late 1956, and this size was later adopted and promulgated as a standard by the System/360. The term 'byte' was coined by mutating the word 'bite' so it would not be accidentally misspelled as bit.
See also nybble.