What determines whether teastaigh requires eclipsis? What about lenition?
Are you referring to the verb teastaigh in general, or only to those conjugations that take the form teastaigh ?
The past indicative theastaigh is lenited unless it’s preceded by a particle that causes eclipsis. Several verbal and relative particles can cause either eclipsis or lenition on a following verb, but few of the eclipsing ones can be used before a past indicative conjugation. I don’t know if any of them could be used before a imperative conjugation; ná, the most common particle (if not the only one) before an imperative, doesn’t mutate, but would prepend an h before an imperative that begins with a vowel.
Ok, thank you. I have not learned the past and future tenses of teastaigh yet; I have only learned the present tense so far. I should have been more specific in my question in that I would like to know the requirements for eclipsis and lenition for teastaigh when in the present tense. Does my question make sense? Please let me know if I need to further clarify.
In the present tense, you eclipse when you follow the question particles an and nach, and you lenite when you follow the negative particle ní.
Teastaíonn sé uaim - I need it
Ní thestaíonn sé uaim - I don't need it (with lenition)
An dteastaíonn sé uaim - Do I need it? (with eclipse)
Nach dteastaíonn sé uaim - Don't I need it? (with eclipse)
Thank you so much! This is just the answer I was looking for. I'll let you know if I have further questions.