in English is:

theism

Mutations

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

Use

y theistiaeth hon
fy theistiaeth i
dy theistiaeth di
ei theistiaeth ef/o
ei theistiaeth hi
ein theistiaeth ni
eich theistiaeth chi
eu theistiaeth nhw/hwy
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