▁ ▁are ▁considered ▁contrast ing ) — in ▁either ▁case , ▁more ▁than ▁any ▁present - day ▁variety ▁of ▁the ▁language . ▁During ▁the ▁ 1 6 th ▁and ▁early ▁ 1 7 th ▁centuries ▁these ▁ph on emes ▁merged ▁differently ▁as ▁they ▁evol ved ▁into ▁those ▁of ▁the ▁different ▁modern ▁dialect s . ▁There ▁were ▁four ▁pairs ▁of ▁vo ic eless ▁versus ▁vo iced ▁s ibil ants : ▁dent al / al ve olar ▁aff ric ates ▁ ▁vs . ▁ ▁( sp elled ▁ ▁or ▁ ▁vs . ▁); ▁dent al / al ve olar ▁fr ic atives ▁ ▁( sp elled ▁ ▁when ▁inter v ocal ic , ▁ ▁otherwise ) ▁vs . ▁ ▁( inter v ocal ic ▁only , ▁sp elled ▁); ▁postal ve olar ▁aff ric ates ▁ ▁( sp elled ▁ ▁vs . ▁; ▁and ▁postal ve olar ▁fr ic atives ▁ ▁( sp elled ▁) ▁vs . ▁. ▁Both ▁ ▁and ▁ ▁were ▁sp elled ▁ ▁before ▁ ▁or ▁), ▁and ▁ ▁elsewhere . ▁It ▁is ▁likely ▁that ▁ ▁de aff ric ated ▁and ▁merged ▁with ▁ ▁before ▁the ▁year ▁ 1 5 0 0 . ▁The ▁main ▁difference ▁between ▁the ▁prest ige ▁dialect ▁of ▁north ▁central ▁Spain ▁and ▁dialect s ▁to ▁the ▁south ▁( such ▁as ▁And alus ian ▁Spanish ) ▁was ▁that , ▁in ▁the ▁north , ▁the ▁dent al / al ve olar ▁continu ants ▁were ▁more ▁ret ract ed ▁than ▁the ▁aff ric ates ▁( the ▁former ▁pair ▁can ▁be ▁represented