Peggy was working. Beidh m ansin. I'll be there. N bheidh sin maith. That won't be good.
Irish nouns are either masculine or feminine.
While some nouns predictably fall into one category or the other, many are random and their gender has to be memorized. According to the Christian Bros. The above forms of the nouns and their articles are used when the nouns are the subject or direct object of a sentence.