"I will not be working on Saturday."
Translation:Cha bhi mi ag obair Disathairne.
bidh is the independent form – it stands on its own in the beginning of the sentece.
bi is the dependent form that comes after particles requiring the dependent form, eg. the negating cha (which also causes lenition) or the interrogative (questioning) am/an.
So it is:
- bidh mi ag obair I will be working,
- cha bhi mi ag obair I will not be working,
- am bi mi ag obair? will I be working?.
In Gaelic verbs have different endings (and sometimes different forms entirely) in independent and dependent positions. Compare the present tense: tha but a bheil (or sometimes older am bheil) and chan eil; or the past tense: bha was but an robh? was? and cha robh was not.