ríagol

Old Irish

ríagol f

rule
- c. 845, St Gall Glosses on Priscian, published in Thesaurus Palaeohibernicus (reprinted 1975, Dublin Institute for Advanced Studies), edited and with translations by Whitley Stokes and John Strachan, vol. II, pp. 49–224, Sg. 9^a22 (Wikisource link)
  Cía for·comam-ni ríagoil sen-Gréc hi scríbunt in dá caractar isnaib ɔsonaib ucut, ro·cruthaigsemmar camaiph immurgu óen charactar – ·f· tar hési ·p· co tinfeth – i n‑epertaib Latinṅdaib.
  Although we preserve the rule of the ancient Greeks in writing the two characters in those consonants, we have, however, formed one character – f instead of p with lenition – in Latin words.

Feminine ā-stem
	Singular	Dual	Plural
Nominative	ríagol^L	ríagoil^L	ríagla^H
Vocative	ríagol^L	ríagoil^L	ríagla^H
Accusative	ríagoil^N	ríagoil^L	ríagla^H
Genitive	*ríaglae^H	ríagol^L	ríagol^N
Dative	ríagoil^L	ríaglaib	ríaglaib
Initial mutations of a following adjective: ^H = triggers aspiration ^L = triggers lenition ^N = triggers nasalization

Old Irish mutation
Radical	Lenition	Nasalization
ríagol also rríagol after a proclitic ending in a vowel	ríagol pronounced with /r(ʲ)-/	unchanged
Note: Some of these forms may be hypothetical. Not every possible mutated form of every word actually occurs.