How to Conjugate the Irregular Latin Verb Sum "To Be"

The Proper Conjugations of Esse

Graffiti reading "civis romanus sum"
"I am a Roman citizen." A proud graffito on via dell'Umiltà.

 CC BY 2.0 by antmoose

The Latin word sum is perhaps among the best known of all the Latin verbs and it is among the hardest to learn. Sum is the present indicative tense of the verb esse, meaning "to be." As with many other living and dead languages, esse is one of the oldest verb forms in Latin, one of the most frequently used of the verbs, one of the most irregular verbs in Latin and related languages. It is also often contracted in casual use (such as in English I'm, that's, they're, he's), becoming almost invisible to the listener.


The progenitor form of "to be" is in the Proto-Indo-European (PIE) language, the parent language of Latin, Greek, Sanskrit, Iranian, Germanic, and indeed most of the languages spoken in all of Europe, India, and Iran. Each of the PIE languages has a form of "to be," perhaps because it is so eminently useful: sometimes "to be" can have an existential significance ("To be or not to be, I think therefore I am"), but also retains its use in everyday language.

In etymological circles, to be is the b-root word, and like all of the b-roots probably is derived from an ancient PIE root, today reconstructed as *h1és-mi (I am). It is also possible that "to be" in Latin derives from the root word *bhuH- meaning "to grow." Other closely related words to esse are asmi in Sanskrit and ešmi in Hittite.

Conguating Sum

 Future PerfectFirstfuerofuerimu

Irregular Verbs and Compounds

There are several other Latin irregular verbs and compound verbs formed from sum.

Eo - to goFio - to become
nolo, nolle, nolui - 'to be unwilling' and malo, malle, malui 'to prefer' are similar.Volo - to wish
Fero - to carrySum - to be
compounds: adsum, desum, insum, intersum, praesum, obsum, prosum, subsum, supersum
Do - to giveEdo - to eat