First Person

Sum: “I am”

Sumus: “We are”

Second Person 

Es: “You (s) are”

Estis: “Y’all are/You (p) are/ You all are”

Third Person

Est: “He, She, It is”

Sunt: “They are”

Now let’s look at the imperfect tense of sum. As with the present, the imperfect-tense forms of esse are irregular. They are:

Singular

Plural

First Person

Eram: “I was”

Eramus: “We were”

Second Person 

Eras: “You (s) were”

Eratis: “Y’all were/You (p) were/ You all were”

Third Person

Erat: “He, She, It was”

Erant: “They were”

Notice that all these forms have as a characteristic vowel the letter a. This is the same a that shows up in the -ba- endings of other imperfect verbs. And as with other imperfect verb forms in Latin, the imperfect of the verb “to be” carries the sense of unfinished, repeated, or habitual action in the past, producing the following translations: “I was,” “I used to be,” “I kept on being”; “you were,” “you used to be,” “you kept on being”, “he, she or it was,” … Pretty obvious. 

Now let’s look at the future tense of sum which is also irregular. Its forms are: 

First Person

Ero: “I will be”

Erimus: “We will be”

Second Person 

Eris: “You (s) will be”

Eritis: “Y’all will be/You (p) will be/ You all will be”

Third Person

Erit: “He/She/It will be”

Erunt: “They will be”

Notice that these forms share a characteristic letter i which is also seen in the -bi- of other future-tense forms. And notice that they also share the same irregularities. The characterizing i disappears in both -bo and ero, and it changes to u in the third person plural -bunt and erunt. Also, just like other future tense forms, the future of the verb “to be” carries the sense of action subsequent to the present: “I will be,” “you will be,” “he will be…” … crazy if we recite all of these forms.

First Person

Possum: I am able

Possumus: We are able

Second Person 

Potes: You are able

Potestis: Ya’ll are able

Third Person

Potest: He/She/It is able

Possunt:They are able

… and the infinitive: posse 

There’s one minor irregularity here which is really not an irregularity. When “t” runs into “s” in Latin, very often the t will change to an “s” and produce the geminate consonant cluster “ss.” So *pot-sum will turn into possum, *pot-sumus will turn into possumus, *pot-sunt will turn into possunt, and *pot-esse will contract down to posse. 

Here is the imperfect tense of possum. Let’s say these forms together:

First Person

Poteram: I was able

Poteramus: We were able

Second Person 

Poteras: You were able

Poteratis: Y'all were able

Third Person

Poterat: He/She/It was able

Poterant: They were able

As you can see, it’s a simple compound of the prefix pot- which means “able” attached onto the imperfect tense forms of the verb “to be.” This tense translates the same way all imperfect tenses translate in Latin: “I was able,” “I could”; “you were able,” “you could”; … and so on. 

Possum also has a future tense which is, as you can see, the expected combination of pot- + ero. Let’s recite this one together also:

First Person

Potero: I will be able

Poterimus: We will be able

Second Person 

Poteris: You will be able

Poteritis: Ya’ll will be able

Third Person

Poterit: He/She/It will be able

Poterunt:They will be able

Let know know if y'all have any questions, comments, concerns, et cetera!