in English is:

grey matter

Mutations

Soft:lwydyn
Nasal:(no mutation)
Aspirate:(no mutation)

Use

y llwydyn hwn
fy llwydyn i
dy lwydyn di
ei lwydyn ef/o
ei llwydyn hi
ein llwydyn ni
eich llwydyn chi
eu llwydyn nhw/hwy
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