There are two ways of saying would in Welsh, using byddwn (south) and baswn (north), which is often contracted to just swn . 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 yn and following verbnouns such as dod , to come , do not mutate.
Affirmative
English Welsh Alt 1 Alt 2 Examples I would baswn i mi faswn i swn i baswn i’n dod you would baset ti mi faset ti set ti baset ti’n dod he would basai fo mi fasai fo sai fo basai fo’n dod she would basai hi mi fasai hi sai hi basai hi’n dod Carys would basai Carys mi fasai Carys sai Carys basai Carys yn dod the girls would basai’r merched mi fasai’r merched sai’r merched basai’r merched yn dod we would basen ni mi fasen ni sen ni basen ni’n dod you would basech chi mi fasech chi sech chi basech chi’n dod they would basen nhw mi fasen nhw sen nhw basen nhw’n dod
Interrogative
English Welsh Alt 1 Alt 2 Examples would I? faswn i? – swn i? faswn i’n dod? would you? faset ti? – set ti? faset ti’n dod? would he? fasai fo? – sai fo? fasai fo’n dod? would she? fasai hi? – sai hi? fasai hi’n dod? would Carys? fasai Carys? – sai Carys? fasai Carys yn dod? would the girls? fasai’r merched? – sai’r merched? fasai’r merched yn dod? would we? fasen ni? – sen ni? fasen ni’n dod? would you? fasech chi? – sech chi? fasech chi’n dod? would they? fasen nhw? – sen nhw? fasen nhw’n dod?
Negative
English Welsh Alt 1 Alt 2 Examples I would not faswn i ddim – swn i ddim faswn i ddim yn dod you would not faset ti ddim – set ti ddim faset ti ddim yn dod he would not fasai fo ddim – sai fo ddim fasai fo ddim yn dod she would not fasai hi ddim – sai hi ddim fasai hi ddim yn dod Carys would not fasai Carys ddim – sai Carys ddim fasai Carys ddim yn dod the girls would not fasai’r merched ddim – sai’r merched ddim fasai’r merched ddim yn dod we would not fasen ni ddim – sen ni ddim fasen ni ddim yn dod you would not fasech chi ddim – sech chi ddim fasech chi ddim yn dod they would not fasen nhw ddim – sen nhw ddim fasen nhw ddim yn dod