possum

Possum (POSS-oom, "I am able, I can") is the ordinary Latin verb for capacity — being able, having power to. It is everywhere. The record holds 28,541 occurrences across 368 works. It clusters, unsurprisingly, in the long prose masters: Livy's Ab Urbe Condita ("From the Founding of the City") carries 1,736; Quintilian's Institutio Oratoria ("The Education of the Orator") 1,074; then three volumes of correspondence — two of Cicero's, the Epistulae ad Familiares ("Letters to Friends," 948) and Letters to Atticus (909), and the Ad Lucilium Epistulae Morales ("Moral Letters to Lucilius," 858) — followed by Cicero's prosecution In C. Verrem ("Against Verres," 723). History, rhetoric, and letters: the word of what men could and could not do.

Lewis & Short (A Latin Dictionary, 1879) glosses it plainly, "to be able," and its entry preserves the seam of the word's making: the old forms potis sum for possum, potis est, potis sunt — the adjective potis ("able, capable") welded to sum ("I am"). To be able was, literally, to be capable. The dictionary cites the archaic surfaces in Plautus, where the older joint still shows.

On ancestry the record is spare: one etymology pointer, noting only that possum is treated in Ernout–Meillet (Dictionnaire étymologique de la langue latine, DELL, 4th ed. 1959) s.v. possum. No reconstructed root is matched in the brief, so none is claimed here.

The citable passages are all inflection and no rest: posset, poterat, possent, poterant, possumus, posse — could, was able, might be able, we are able, to be able — drawn from the opening books of Livy. Even in a concordance the verb refuses to sit still.

If a word appears this often and everywhere, does it name a thing at all, or only the hinge on which every other thing turns?