1. What is the 'yes' answer for a question beginning with 'Wyt ti wedi...?' or 'Dach chi wedi...?' Most speakers use 'Do' or 'Naddo' here, although more traditionally, the answer would be 'ydw' or 'nac ydw'. 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.