3. Some nouns in ar drop the a, and add to the nom. sing. the syllable aich; and then the final a becomes e, to correspond to the preceding small vowel; as, leabhar m. a book, n. p. leabhraiche; tobar m. a well, n. p. tobraiche; lann. f. an enclosure, inserts d, n. p. lanndaiche. Piuthar f. a sister, from the g. s. peathar, has n. p. peathraiche; so leaba f. a bed, g. s. leapa, n. p. leapaiche. Bata m. a staff, n. p. batacha; la or latha a day, n. p. lathachan or laithean.
4. Some polysyllables in ach add e or ean to the genitive singular; as, mullach m. summit, g. s. mullaich, n. p. mullaichean; otrach m. a dunghill, n. p. otraichean; clarsach f. a harp, n. p. clarsaichean; deudach f. the jaw, n. p. deudaichean. So sliabh m. a moor, g. s. sleibh, with t
inserted, n. p. sleibhte. Sabhul m. a barn, g. s. sabhuil, n. p. saibhlean, contracted for sabhuilean.
The following Nouns form their Nominative Plural irregularly: Dia m. God, n. p. dée or diathan; scian f. a knife, n. p. sceana or scinichean; sluagh m. people, n. p. sloigh; bo. f. a cow, n. p. ba.
Genitive. 1. Monosyllables, and nouns which form their nominative plural like the genitive singular, have the genitive plural like the nominative singular; as, geug f. a branch, g. p. geug; coimhearsnach m. a neighbour, g. s. and n. p. coimhearsnach.
2. Polysyllables which have their nominative plural in a or an, form the genitive like the nominative; leabhar m. a book, n. p. and g. p. 'leabraichean'—When the nominative plural is twofold, the genitive is so too; as 'fear' n. a man, n. p. fir, or sometimes feara, g. p. fear or feara.
Cu m. a dog has its g. p. con; caora f. a sheep, g. p. caorach; sluagh m. people, g. p. sluagh or slogh.
Dative. The dative plural is formed either from the nominative singular or from the nominative plural. If the nominative plural ends in a consonant, the dative plural is formed by adding ibh to the nominative singular; as, crann m. a tree, n. p. croinn, d. p. crannaibh; mac m. a son, n. p. mic, d. p. macaibh. If the nominative plural ends in a vowel, the final vowel is changed into ibh; as, tobar a well, n. p. tobraiche, d. p. tobraichibh.
2. Monosyllables ending in an aspirated consonant, which have their nominative plural like the genitive singular, form their dative plural like the nominative plural; as, damh an ox, g. s. and n. p. daimh, d. p. daimh, not damhaibh; fiadh m. a deer, g. s. and n. p. and d. p. feidh. So sluagh m. people, host, g. s. sluaigh, n. p. and d. p. sloigh. Nouns ending in ch, of three or more syllables, form their dative plural like the nominative plural, rather than in ibh; as, coimhearsnach m. a neighbour, d. p. coimhearsnaich rather than coimhearsnachaibh; phairiseach m. a Pharisee, d. p. phairisich rather than phairiseachaibh.