1. Irregular Verbs: “esse” and “posse” Present System
Magister Henderson
Latin II

2. About “sum, esse” (to be)
The verb sum, esse is a linking verb, meaning it takes a predicate nominative rather than a direct object.
It is irregular in all three forms of the present system (present, imperfect, and future).
Present Tense
Singular
Plural
First Person
sum
= I am
sumus
= we are
Second Person es
= you are
estis
Third Person
est
= he / she / it is
sunt
= they are

3. Imperfect and Future of “esse”
Imperfect Tense
Singular
Plural
First Person
eram
= I was
erāmus
= we were
Second Person
erās
= you were
erātis
Third Person
erat
= he / she/ it was
erant
= they were
Future Tense
Singular
Plural
First Person
erō
= I will be
erimus
= we will be
Second Person
eris
= you will be
eritis
Third Person
erit
= he will be
erunt
= they will be

4. About “possum, posse” (to be able)
Compound form of potis and sum, esse.
The prefix “pot-” is used for forms of esse that begin with “s” (sum, sumus, and sunt).
For forms that begin with “e” (es, est, and estis), the prefix assimilates to “pos-”.
Present Tense
Singular
Plural
First Person
possum
= I can
possumus
= we can
Second Person
potes
= you can
potestis
Third Person
potest
= he / she / it can
possunt
= they can

5. Imperfect and Future of “posse”
All the imperfect and future tense forms of posse use “pot-” since all forms of esse in the imperfect and future tenses begin with the letter “e”.
Imperfect Tense
Singular
Plural
First Person
poteram
= I could
poterāmus
= we could
Second Person
poterās
= you could
poterātis
Third Person
poterat
= he / she / it could
poterant
= they could
Future Tense
Singular
Plural
First Person
poterō
= I will be able
potermus
= we will be able
Second Person
poteris
= you will be able
poteritis
Third Person
poterit
= he will be able
poterunt
= they will be able

6. Translating the verb “posse”
To translate possum, posse use either the defect verb “can” or the phrase “be able (to)”.
Defective verbs are verbs that are missing forms. For the missing forms you will need to use some form of “be able (to)”.
Form
Latin
Verb Translation
Phrase Translation
Infinitive
posse
n/a
= to be able (to)
Present tense
possum
= I can
= I am able (to)
Imperfect Tense
poteram
= I could
= I was able (to)
Future Tense
poterō
= I will be able (to)