Buḋ or ḃus is never used in the spoken language, and scarcely ever in writing, except when a superlative adjective or adverb occurs in a sentence, the verbs of which are in the Future Tense.
337. In the Present Tense the verb IS is omitted after all particles except MÁ, if: as, Is mé an fear. I am the man; Ní mé an fear. I am not the man.
338. In the Past Tense BA is usually omitted after particles when the word following BA begins with a consonant: as, Ar ṁaiṫ leat an áit? Did you like the place? Nár ḃeag an luaċ é? Was it not a small price? Ba is not usually omitted when the following word begins with a vowel or f, but the a is elided: as, Níor ḃ’ é sin an sagart. That was not the priest. Notice that the word immediately after ba or baḋ, even when ba or baḋ is understood, is usually aspirated when possible.
(b) In Dependent Sentences.
339. Present Tense.—Ab is used instead of is after gur, meaning “that”; as, measaim gurab é sin an fear. I think that is the man. Before a consonant ab is usually omitted; as, deir sé gur mise an fear. He says that I am the man. Ab is always omitted after naċ, that … not. Saoilim naċ é sin an rí. I think that is not the king.
340. Past Tense.—The word ba or baḋ becomes ḃ’ in dependent sentences and is usually joined to the
