What are the -IR verbs that have a change to a letter "i" in them and what is that change called?
For Example: the verb "repetir" changes to "repito", and the same goes for divertir. I want to know because I'm currently learning vosotros commands and all these -IR verb changes with the letter "i' are getting confusing. What is this change even called? I've heard someone reference it as "the second change" or something along those lines?
I've never heard them called anything, but e to i stem changes with 3rd conjugation verbs (-ir).
(e to ie stem changes are usually taught first, which is where the "2nd change" reference may have come from.)
Just to add a comment, you are referring to negative vosotros commands, aren't you? (The ones that use the subjunctive endings?) The stem changes don't play any part in with affirmative vosotros commands as they just remove the r from the infinitive (not a conjugated stem) and replace it with a d. comer=comed decir-decid. The negative vosotros command are formed from the present subjunctive tense which in turn used the 1st person, present indicative tense so they would be effected by stem changes.
yo form (indicative) (this is where the stem changing starts)
to form present subjunctive (yo) from 1st person, sing. indicative
Negative vosotros (áis) command
the affirmative vosotros command for pedir (no stem change effect)