u/AaryanShahFan1478

I've been learning Latin for about 2 years now, and all throughout I've noticed a strange pattern of ablaut/umlaut in verbs, whereby the thematic vowel A changes to E or I, usually when prefixed or in the perfect tenses. For example:

Facere --> Feci

Agere --> Egi

Cadere --> Accidere

Scandere --> Ascendere

Tangere --> Contingere

I've always assumed this was some sort of umlaut or i-mutation, like what happened in a lot of Germanic languages, but I want a second opinion. Why does this happen, and is there any regularity or predictability to this? Why does it happen in some verbs and not others (like Vadere)?

This has been bugging me for a while. Thank you!