UTF-16 (16-bit UCS/Unicode Transformation Format) is a variable-length character encoding for Unicode, capable of encoding the entire Unicode repertoire, by mapping each character (or code point) to a sequence of 16-bit code units. For characters in the Basic Multilingual Plane (BMP) the encoding is a single code unit equal to the code point. For characters in the other planes the encoding is a pair of code units called a surrogate pair.