There are two ways of saying would have in Welsh, using byddwn … wedi (south) and baswn … wedi (north), which is often contracted to just swn … wedi . It’s best to be aware of both, and let local usage dictate which one you use.
As both are forms of bod , these auxiliary verbs both use wedi and following verbnouns such as bwyta , to eat , do not mutate.
Affirmative
English Welsh Alt 1 Alt 2 Examples I would have baswn i wedi mi faswn i wedi swn i wedi baswn i wedi bwyta you would have baset ti wedi mi faset ti wedi set ti wedi baset ti wedi bwyta he would have basai fo wedi mi fasai fo wedi sai fo wedi basai fo wedi bwyta she would have basai hi wedi mi fasai hi wedi sai hi wedi basai hi wedi bwyta Carys would have basai Carys wedi mi fasai Carys wedi sai Carys wedi basai Carys wedi bwyta the girls would have basai’r merched wedi mi fasai’r merched wedi sai’r merched wedi basai’r merched wedi bwyta we would have basen ni wedi mi fasen ni wedi sen ni wedi basen ni wedi bwyta you would have basech chi wedi mi fasech chi wedi sech chi wedi basech chi wedi bwyta they would have basen nhw wedi mi fasen nhw wedi sen nhw wedi basen nhw wedi bwyta
Interrogative
English Welsh Alt 1 Alt 2 Examples would I have? faswn i wedi? – swn i wedi? faswn i wedi bwyta? would you have? faset ti wedi? – set ti wedi? faset ti wedi bwyta? would he have? fasai fo wedi? – sai fo wedi? fasai fo wedi bwyta? would she have? fasai hi wedi? – sai hi wedi? fasai hi wedi bwyta? would Carys have? fasai Carys wedi? – sai Carys wedi? fasai Carys wedi bwyta? would the girls have? fasai’r merched wedi? – sai’r merched wedi? fasai’r merched wedi bwyta? would we have? fasen ni wedi? – sen ni wedi? fasen ni wedi bwyta? would you have? fasech chi wedi? – sech chi wedi? fasech chi wedi bwyta? would they have? fasen nhw wedi? – sen nhw wedi? fasen nhw wedi bwyta?
Negative
English Welsh Alt 1 Alt 2 Examples I would not have faswn i ddim wedi – swn i ddim wedi faswn i ddim wedi bwyta you would not have faset ti ddim wedi – set ti ddim wedi faset ti ddim wedi bwyta he would not have fasai fo ddim wedi – sai fo ddim wedi fasai fo ddim wedi bwyta she would not have fasai hi ddim wedi – sai hi ddim wedi fasai hi ddim wedi bwyta Carys would not have fasai Carys ddim wedi – sai Carys ddim wedi fasai Carys ddim wedi bwyta the girls would not have fasai’r merched ddim wedi – sai’r merched ddim wedi fasai’r merched ddim wedi bwyta we would not have fasen ni ddim wedi – sen ni ddim wedi fasen ni ddim wedi bwyta you would not have fasech chi ddim wedi – sech chi ddim wedi fasech chi ddim wedi bwyta they would not have fasen nhw ddim wedi – sen nhw ddim wedi fasen nhw ddim wedi bwyta