-aeth

• -iaeth

From Proto-Brythonic *-aɨθ, from Insular Celtic *-axtā, suffixal use of Proto-Celtic *axtā. Cognate with Cornish -eth, Breton -ezh, Irish -acht, Scottish Gaelic -achd and Manx -aght.

• (North Wales, standard, colloquial) IPA^(key): /aɨ̯θ/
  • (North Wales, colloquial) IPA^(key): /ɛθ/, /aθ/
• (South Wales, standard) IPA^(key): /ai̯θ/
  • (South Wales, colloquial) IPA^(key): /ɛθ/

-aeth f (plural -aethau)

1. Forms abstract nouns.

   ‎aelod (“member”) + ‎-aeth → ‎aelodaeth (“membership”)

   ‎cyflog (“wage”) + ‎-aeth → ‎cyflogaeth (“employment”)

   ‎meddyg (“doctor”) + ‎-aeth → ‎meddygaeth (“medicine”)

   ‎amau (“to doubt”) + ‎-aeth → ‎amheuaeth (“doubt”)

2. territory controlled by, -ship, -age, -y, -dom

   ‎ymherodr (“emperor”) + ‎-aeth → ‎ymerodraeth (“empire”)

   ‎esgob (“bishop”) + ‎-aeth → ‎esgobaeth (“diocese, bishopric”)

• With names of leaders, -aeth can be both concrete and abstract, for instance iarllaeth (“earldom”) is both the rank of being an earl and the territory controlled by one.

• Most nouns in -aeth are feminine. Common exceptions are gwasanaeth (“service”) and hiraeth (“longing, homesickness”).

• R. J. Thomas, G. A. Bevan, P. J. Donovan, A. Hawke et al., editors (1950–present), “-aeth”, in Geiriadur Prifysgol Cymru Online (in Welsh), University of Wales Centre for Advanced Welsh & Celtic Studies
• Morris Jones, John (1913) A Welsh Grammar, Historical and Comparative, Oxford: Clarendon Press, § 143 iii 2