The word joiner (WJ) is a code point in Unicode used to separate words when using scripts that do not use explicit spacing. It is encoded since Unicode version 3.2 (released in 2002) as U+2060 WORD JOINER (HTML ⁠). The word joiner does not produce any space, and prohibits a line break at its position.
The word joiner replaces the zero-width no-break space (ZWNBSP), a deprecated use of the Unicode character at code point U+FEFF. Character U+FEFF is intended for use as a Byte Order Mark at the start of a file. However, if encountered elsewhere it should, according to Unicode, be treated as a "zero-width non-breaking space." The deliberate use of U+FEFF for this purpose is deprecated as of Unicode 3.2, with the word joiner strongly preferred.