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

Mood Tense Person Singular Plural
indicative Present First sum sumus
Second es estis
Third est sunt
Imperfect First eram eramus
Second eras eratis
Third erat erant
Future First ero erimus
Second eris eritis
Third erit erunt
Perfect First fui fuimus
Second fuisti fuistis
Third fuit fuerunt
Pluperfect First fueram fueramus
Second fueras fueratis
Third fuera fuerant
Future Perfect First fuero fuerimu
Second fueris fueritis
Third fuerit fuerint
Subjunctive Present First sim simus
Second sit sitis
Third sit sint
Imperfect First essem essemus
Second esses essetis
Third esset essent
Perfect First fuerim fuerimus
Second fueris fueritis
Third fuerit fuerint
Pluperfect First fuissem fuissemus
Second fuisses fuissetis
Third fuisset fuissent

Irregular Verbs and Compounds

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

Eo - to go Fio - to become
nolo, nolle, nolui - 'to be unwilling' and malo, malle, malui 'to prefer' are similar. Volo - to wish
Fero - to carry Sum - to be
compounds: adsum, desum, insum, intersum, praesum, obsum, prosum, subsum, supersum
Do - to give Edo - to eat