I thought dillad was one of those words which have the plural as the basic form. So why isn’t it “Maen y dillad yn ddrud” then? Do people just not percieve dillad as plural anymore? Does that mean the singulative dilledyn has fallen out of use?
Because "Maen" is only used with "nhw". e.g "Maen nhw'n ddrud" (They are expensive) whereas "Mae" is used with all nouns no matter if they are plural or not i.e Mae'r dillad yn ddrud" along with "Mae'r cathod yn dew" (The cats are fat). etc