D - (also a mutation of T; e.g. "Teilo" becomes "deilo" in "Llandeilo")

Word element	Meaning	Example of use (sound file links underlined)
Dafydd	David
dan	see tan	Dan-y-bryn
dar, (plural deri)	oak
darren	see tarren	Ynysydarren
dau, ddau, ddeu, (feminine dwy, ddwy)	two
Dawe	see Tawe	Pontardawe
dawel	calm
de	south
deg	fair, beautiful	Gellideg
Deilo	see Teilo	Llandeilo
derwen, (plural derw)	oak	Derwen Fawr
deu	see dau
Dewi	David	Dewi Sant (St David's)
diffwys	precipice, desolate place
din	hill fortress	Dinmael
dinas	hill fortress, city	Dinas Mawddwy
dir	land
diserth	hermitage, wilderness
dol, (plural dolau, dolydd)	meadow, water meadow	Dolgellau
domen	see tomen	Domen yr Allt
don	wave
draen, (plural drain)	thorn
dreath	see traeth	Penrhyndeudraeth
dre	see tre	Dre-fach
dref	see tref
dri	see tri
drindod	trinity	Llandrindod
drum	see trum
drws	gap, narrow pass	Drws-y-nant
du, (feminine ddu)	black; dark	Cwmdu
Dudno	see Tudno	Llandudno
Dulais	name of river, e.g. in Carmarthenshire and Glamorgan	Aberdulais
Dulas	river in (e.g.) Breconshire	Llanddulas
dwfr,dwr	water
dwy	see dau
dy	see ty
dyffryn	valley	Dyffryn
Dyfi	Dovey - river in Merioneth/Montgomeryshire	Aberdyfi
Dyfnant	river in
Dyfrdwy	Dee - river in Denbigh/Merionethshire	Afon Dyfrdwy
dyrys	difficult
Dysilio	see Tysilio
dywyll	dark

DD - (a mutation of D; e.g. "Dulais" becomes "ddulais" in "Pontarddulais")

Word element
Meaning Example of use
(sound file links underlined)

ddau see dau

dderwen, (plural dderw) see derwen Maesydderwen

ddeu see dau Llanddeusant

Ddewi see Dewi

ddinas see dinas

ddu see du Dduallt

ddwr see dwr

ddwy see dau