What is the correct spelling please? Cwm or cŵm for valley? I have found both cwm and cŵm spelt randomly on line.
So then I logged onto SSIW and found this message from @deborah
"Feb 9 - There are a few north Walian residents of Cwmderi in Pobol y Cŵm "
Also, when or where would we use dyffryn please?
Similarly, I have found cwtch, cŵtch - cwtsh, cŵtsh a problem.
Most of my local friends in Carmarthenshire use cwm and cwtch but it seems to vary in different parts of Wales.
cwm is the correct spelling. Generally cwm describes a narrow valley whereas dyffryn describes a wider valley.
The spelling of cwtch does vary between areas. Phonetically cwtsh is the more correct and I think cwtch is probably a ‘Wenglish’ spelling.
Thank you very much Siaron. Thats really helpful.
My friend who was born in north Wales, left for overseas as a child, likes to spell cwtsh as cŵtsh so he’s nearly right. Its because he likes the ŵ. I need to find other Welsh words for him with a roof or ’ on top. I don’t know the correct expressions for them either.
I am currently studying the Welsh governments list of accepted place names too, in an effort to find more words using them. 
Diolch yn fawr!
https://www.welshlanguagecommissioner.wales/standardised-welsh-place-names
The common name for the ^ accent in Welsh is indeed to bach - ‘little roof’, although it’s official name is acen grom - bent/curved accent - or circumflex accent in English. It’s used to make the vowel sound longer, which is why to my ear cwtsh (cutsh) is more correct than cŵtsh (cootsh).
Here’s a (non-exhaustive) list I found in a quick web search in which the ^ plays a significant role:
mor (so) – môr (sea)
llen (curtain) – llên (literature)
tan (until, under) – tân (fire)
hyn (this) – hŷn (older)
man (place) - mân (small, fine)
ffon (stick) - ffôn (phone)
gwn (gun) - gŵn (gown), gŵn (cŵn - dogs)
ton (wave) - tôn (tone, tune)
fer (ber (f) - short) - fêr (mêr - marrow)
dim (nothing) - dîm (tîm - team)
glan (bank, shore; up) - glân (clean, holy)
gan (with) - gân (cân - song)
and I also found this which is quite handy:
and (you’ve probably come across these already) some examples of place names -
Caersŵs, Aberdâr, Pentredŵr, Llannerch-y-môr.
Wow! Thankyou so much Siaron. Thats very helpful and I’m sure it will help other people too! Especially helpful for my friend to understand is the pronunciation. I will copy paste it.
I only got about half way through our language commissioner’s list yesterday and fell asleep! I now feel more motivated to continue now.
Ti’n seren Siaron! 
Sorry to mislead you. I’m not sure how that to bach popped on there 
No worries at all, 
I am easily confused anyhow. It also motivated me to get going with my Welsh again. So thank you!
