When I was learning Spanish, I came across the fact that Spanish verbs have three classes: AR, ER, and IR. I notice that more of them have the AR verb ending.
The verb endings are the same in Latin, but is there a root from Proto-Indo-European that determines these verb endings? If there is, it is probably not 100% across the board because some ER/ERE verbs in Latin got turned into IR verbs. If there isn't an obvious one, then is there a tendency for AR verbs to have one type of trait(s) and the other types to have another trait or group of traits?
What I mean by "where do they come from" is in part about if there are words that are roots.
