2. If the nominative suffered a syncope in forming the genitive, or if the last vowel of the genitive is broad, the dative is like the nominative; as, buidheann f. _a company_, g. s. buidhne, d. s. buidheann; piuthar f. _a sister_, g. s. peathar, d. s. piuthar.
The _Vocative_ of masc. nouns is like the genitive; of feminine nouns is like the nominative; as, bàs m. _death_, g. s. bàis, v. s. bhais; cu m. _a dog_, g. s. coin, v. s. choin; grian f. _the sun_, v. s. ghaoth. { 49}
_Nominative._ Masculine nouns which insert _i_ in the gen. sing. have their nom. plur. like the gen. sing.; as, oglach m. _a servant_, g. s. oglaich, n. p. oglaich; fear m. _a man_, g. s. and n. p. fir. Many of these form their nom. plur. also by adding a short _a_ to the nominative singular. Other masculine nouns, and all feminine nouns, have their nom. plural in _a_, to which _n_ is added, _euphoniæ causa_, before an initial vowel[37].
_Particular Rules_ for forming the Nom. Plur. in _a_ or _an_.
1. By adding _a_ to the nom. singular; as, dubhar m. _a shadow_, n. p. dubhara; rioghachd f. _a kingdom_, n. p. rioghachdan. Under this Rule, some nouns suffer a syncope; as, dorus m. _a door_, n. p. dorsa for dorusa.
2. Nouns ending in _l_ or _nn_, often insert _t_ before _a_; as, reul m. _a star_, n. p. reulta; beann f. _a pinnacle_, n. p. beannta. So lòn m. _a marsh_, n. p. lòintean.
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_ { 50} inserted, n. p. sleibhte. Sabhul m. _a barn_, g. s. sabhuil, n. p. saibhlean, contracted for sabhuilean.