In French, a 'liaison' is when two words are linked together in speech (or "liaised") instead of being pronounced seperately.
Silent consonants can become pronounced during liaisons, for example, the -s in "les" is normally silent but becomes an audible -z in a liaison:
|-S becomes a Z sound||-D becomes a T sound|
|-X becomes a Z sound||-F becomes a V sound|
Pronunciation guides often use 'tie' symbol (or an underscore) instead of a space to show when a liaison occurs in speech.
There are three types of liaisons -
Mandatory liaisons: liaisons every French person will pronounce
Forbidden liaisons: these are liaisons which would never be said by a French native (but might be tempting)
Optional liaisons: some liaisons depend on social background, age, mood and tradition. In this section ‘over liaising’ can sound precious.
See also: Élision