1. What is the 'yes' answer for a question beginning with 'Wyt ti wedi...?' or 'Dych chi wedi...?' The answer is traditionally 'ydw' or 'nac ydw' but you may well hear 'Do' or 'Naddo' too. Both are acceptable when writing or speaking.

2. Mae treiglad trwynol (nasal mutation) ar ôl fy ('my') ac ar ar ôl yn ('in')

p > mh
pen > fy mhen i
Porthcawl > ym Mhorthcawl

t > nh
tŷ > fy nhŷ i
Treorci > yn Nhreorci

c > ngh
cath > fy nghath i
Caerdydd > yng Nghaerdydd

b > m
brawd > fy mrawd i
Bangor > ym Mangor

d > n
doctor > fy noctor i
Dolgellau >yn Nolgellau

g > ng
gwaith > fy ngwaith i
Gwent > yng Ngwent

Note that the 'yn' changes to 'ym' or 'yng' to blend with the start of the following word.