What is "soft hyphen"

n. the symbol represented by code U+00AD. It is defined by http://en.wikipedia.org/wiki/Unicode as a generally invisible character that allows manual specification of a place where a hyphenated break is allowed without forcing a line break in an inconvenient place if the text was later reflowed.

In computing and typesetting, a soft hyphen (ISO 8859: 0xAD, Unicode , HTML: ­ ­) or syllable hyphen (EBCDIC: 0xCA), abbreviated SHY, is a code point reserved in some coded character sets for the purpose of breaking words across lines by inserting visible hyphens. Two alternative ways of using the soft-hyphen character for this purpose have emerged, depending on whether the encoded text will be broken into lines by its recipient, or has already been preformatted by its originator.