Pronounced ter-eh-SHAY, but with the "sh" said while the tip of the tongue is close to the roof of the mouth.Taken from http://en.wikibooks.org/wiki/Basque/Pronunciation :"'S' is probably the trickiest sound of all. It is not like the English 's', but rather like the one used in Castillian Spanish. It sort of sounds like English 'sh', but is much softer. In effect, it is produced by putting the tip of your tongue at the back of your top front teeth when saying 's'. It takes a bit of practice."