§ 6 Rules for Initial Mutations
1. The Second State.
a. A feminine singular or masculine plural noun (or adjective used as a noun) preceded by the definite article an, the, or the numeral idn, one, has its initial in the second state.
b. An adjective which follows and qualifies a feminine singular noun, has its initial in the second state.
c. A noun preceded by an adjective qualifying it, of whatever gender or number, has its initial in the second state.
d. If the adjective preceding and qualifying a feminine singular noun follows the article an, the, the initial of the adjective is also in the second state.
e. A noun in the vocative preceded by the particle a, O (expressed or omitted for the sake of verse), has its initial in the second state.
f. The possessive pronouns dha, thy, and e, his, are followed by words, whether nouns, adjectives, or verbal nouns (infinitives) in the second state. The form ’th, thee or thy, generally puts the word which follows in the second state, but sometimes in the fourth, or changes b to f, not v.
g. The verbal prefix ă (older y, yth), is generally followed by a verb in the second state.
h. The verbal particles a and re and the interrogative particle a are followed by a verb in the second state.
i. The prepositions a, der or dre, dhô, heb, re, and war, and compound prepositions ending in any of them, are followed by words in the second state.
k. The conjunctions tre, tro, that, pan, when, erna, until, hedre, whilst, are followed by the second state.
l. The adverbial particle en is followed generally by an adjective in the second state.
m. The adverbs pŭr, very, ni, na, not, fraga, why, fatla, how, are followed by initials in the second state.
2. The Third State.
a. The possessive pronouns ow, my, î, her, and aga, their, are followed by words in the third state.
b. Ma, may, that, are sometimes followed by verbs in the third state, and sometimes by a variant, g becoming h, and gw becoming wh.
3. The Fourth State.
a. The particle ow, which forms the present participle, is followed by a verbal noun (or infinitive) in the fourth state.
b. The conjunctions a, mar, mara, if, are followed by verbs in the fourth state.
c. The adverb maga, as (in “as well,” etc.) is followed by an adjective in the fourth state.
d. Sometimes an adjective beginning with d, when preceded by the adverbial particle en, has its initial in the fourth state, and rarely a noun beginning with d, when it follows in the appositional genitive a word ending in th.
e. The verbal prefix ă (y), when followed by verbs whose radical initial is d, often changes that initial to the fourth state, and in the case of those beginning with gw to wh. The conjunction ken, though, does the same.
f. The third form of the second personal pronoun singular ’th not infrequently changes the initial of a verb beginning with d to the fourth state, and that of one beginning with g or gw to wh. It also sometimes changes b to f.
The exact usage of the mutations is not very clear, for even the older writers used them rather wildly, but the above rules are the general principles of them. There are valuable notes on their phonetic principles in Dr. Whitley Stokes’s notes to St. Meriasek, and in a paper of additional notes which he published later. In the latest Cornish there was a tendency to use the second state after nearly anything, especially prepositions, except the few words which govern the other two mutations.