genitive plural is formed by dropping the i, as súil, an eye, gen. pl. súl; fuaim, a sound, gen. pl. fuam, &c.
For a list of nouns ending in a broad consonant belonging to this declension, see Appendix II.
THIRD DECLENSION.
91. The 3rd declension includes (1) personal nouns ending in óir (all masculine), (2) derived nouns in aċt or aċd (feminine), (3) other nouns ending in consonants which are, as a rule, masculine or feminine according as they end in broad or slender consonants.
92. The genitive singular is formed by adding a. If the last vowel of the nominative be i preceded by a broad vowel, the i is usually dropped in the gen., as toil, a will, gen. tola.
93. The nominative plural is usually the same as the genitive singular; but personal nouns ending in óir add í or iḋe to the nominative singular.
94. Most of the derived nouns in aċt, being abstract in meaning, do not admit of a plural. Mallaċt, a curse, and a few others have plurals. Fuaċt, cold, although an abstract noun in aċt, is masculine.
95. The vowels of the nominative often undergo a change in the formation of the genitive singular. These changes are just the reverse of the vowel changes of the 1st and 2nd declensions (see pars. 60 and 78.
