Sum, Esse, Fui and the compounds

[AureliaeLacrimae]

Sum, esse, fui - to be

This is one of the irregular verbs. All of the compounds of sum, esse, fui follow the same pattern like this verb.

Present Active Tense:

sum      I am

es        you are

est        he/she/it is

sumus  we are

estis      you are

sunt      they are

Here's a list of the compounds:

absum, abesse, afui                -  I am absent

adsum, adesse, adfui                -  I am present

desum, deesse, defui + D          -  I fail

insum, inesse, + D                  -  I am in

intersum, interesse, interfui      -  I am among/I am a part of

praesum, praesse, praefui        -  I am at the head of

prosum, prodesse, profui + D    -  I benefit

subsum, subesse                      -  I am under

supersum, superesse, superfui    -  I survive

It is very common that adfui is written as affui as well. It's not a mistake - that is the later form when the consonants became similar to each other. The same case is with a lot of other verbs, especially the prefix ad- in combination with f (it becomes aff), but more about this later.