any particular instances where 'gwyl' is more proper to use than 'sant'? or just preference?
thanks as always.
"Gŵyl" means "Festival" which we use for "Saint David's day". It can't be used to mean "Saint".
In this context, dydd gŵyl is a saint's feast-day or festival day. Dewi refers to Dewi Sant.
No. Dewi Sant is such an important figure in Welsh tradition that he is known as Dewi Sant (Dewi the Saint) rather than just Sant Dewi.
His saint's day is dydd Gŵyl Dewi - no Sant.