addo

Addo, addere, addidi, additum is third conjugation, ad plus do, and unlike its parent it conjugates as a normal third conjugation verb rather than keeping the odd short-vowel forms of do. What is added stands in the accusative; what it is added to takes the dative or ad with the accusative.

Adde quod, "add the fact that", is a standard way of piling on an argument in both prose and verse, and worth recognising as a fixed phrase rather than parsing from scratch each time. The reduplicated perfect -did- runs through the whole family: reddidi, tradidi, condidi, perdidi. English add, addition and additive follow directly.