Auxiliary verb sum,esse,fui
The auxiliary verb sum,esse,fui is irregular and has two present stems, visible from the first two forms, sum and esse. Shorter stem s- is always followed by the vowel -u-, but the longer stem es- comes without the vowel before the consonants s or t.
The Present Tense of the Auxiliary Verb
| Singular | Present Tense | Plural | Present Tense |
| sum | I am | sumus | We are |
| es | You are (Singular) | estis | You are (Plural) |
| est | He, she, it is | sunt | They are |
Interrogative Form
Interrogative form consists of the particle –ne, which is written together with the form of the verb.
| Singular | Present Tense – Interrogative | Plural | Present Tense – Interrogative |
| sumne? | Am I? | sumusne? | Are we? |
| esne? | Are you? (Singular) | estisne? | Are you? (Plural) |
| estne? | Is he? (she, it) | suntne? | Are they? |
Esne certa? – Are you sure? Certa sum. – I am sure.
Estisne certae? – Are you sure? Certae sumus. – We are sure.
Negative form
The negative particle non is added in front of the verb.
| Singular | Present Tense – Negative | Plural | Present Tense – Negative |
| non sum | I am not | non sumus | We are not |
| non es | You are not (Singular) | non estis | You are not (Plural) |
| non est | He, she, it is not | non sunt | They are not |
Non sumus certae. – We are not sure.
The Imperative Mode of the Auxiliary Verb
The simple form of the imperative mode has only the second person of singular and plural. The singular form is equal to the longer stem, while the plural form has the ending -te.
| Singular | Imperative | Plural | Imperative |
| es! | be! (one person) | este! | be! (more than one person) |
The Infinitive
The second form of the verb sum,esse,fui is its infinitive (esse – to be)
Some words used in this lesson
- sum,esse,fui – to be
- cautus,-a,-um – careful, cautious
- machina,-ae,f. – machine
- periculosus,-a,-um – dangerous, perilous
- anima,-ae,f. – soul
- alea,-ae,f. – die (pl. dice)
- historia,-ae,f. – history
- magistra,-ae,f. – teacher (feminine)
- vita,-ae,f. – life
- spes,-ei,f. – hope (noun of the fifth declension)
- potentia,-ae,f. – might, power
- certus,-a,-um – sure
Historia est magistra vitae.
Cicero, de oratore
Alea iacta est.
caesar
Dum anima est, spes est.
erasmus
Scientia potentia est.
francis bacon
