The Irregular Latin Verb Possum (To Be Able): Conjugation & Uses
The verb possum “to be able” appears frequently in Latin, but it is also very irregular. Keep reading to learn how to conjugate – and use – possum.
Possum is built off the verb sum (to be), and in this post I will assume that you are already familiar with sum. If you are not, please read this post about sum first.
Still with me? All right. Time to learn everything you need to know about possum!
How to conjugate the Latin verb possum
When learning a new Latin verb, you should always take a look at the principal parts. Here are the principal parts of possum:
possum, posse, potuī
Possum lacks a fourth principal part, and the first two principal parts look unusual. Usually, the second principal part indicates the verb’s conjugation, but that won’t work here.
This is because possum is an irregular verb. It does not belong to any of the four Latin verb conjugations.
The verb possum is a contracted form of potis sum, “I am able.” The adjective potis, e – which means “able, capable, possible” – was rarely used in Classical Latin on its own, but it survived in abbreviated fashion in possum.
Potis sum “I am able” became potsum and then possum. Potis es “you are able” became potes. And so forth. As you can see, possum depends on the verb sum for these present tense forms.
It turns out that the present system of possum is irregular, but based on sum. The perfect system, on the other hand, is entirely regular and thus is not based on sum.
Let’s look at the concrete conjugations, and you will see what I mean.
Present System (Indicative)
The present system of possum is entirely built off sum. This is good news, because it means that if you have already memorized the conjugation of sum, it will be easy to learn the conjugation of possum.
The present system includes the present, imperfect, and future indicative tenses. To conjugate possum in each of these tenses, simply add pos– or pot– onto the beginning of sum.
You add pos– if the form of sum begins with S, and pot– if it begins with E.
Here is the present indicative of possum along with its translation:
I am able, I can
we are able, etc.
you are able, you can
you (y’all) are able, etc.
he/she/it is able, etc.
they are able, etc.
Possum also has a present infinitive, posse. Posse means “to be able.”
Here is the future indicative of possum:
I will be able
we will be able
you will be able
you (y’all) will be able
he/she/it will be able
they will be able
Finally, here is the imperfect indicative of possum:
I was able, I could
we were able, etc.
you were able, you could
you (y’all) were able, etc.
he/she/it was able, etc.
they were able, etc.
That wasn’t so bad, was it? All of these forms come directly from sum.
If you are a beginning student, you may wish to stop reading here and jump down to the uses of possum. If you are in the intermediate or advanced stage, keep reading to learn about the perfect system and the subjunctive tenses.
Present System (Subjunctive)
The present system also includes the present and imperfect subjunctive. The present subjunctive of possum is simply the present subjunctive of sum with an initial pos-.
The imperfect subjunctive actually follows the standard rules: add the active personal endings to the present infinitive. In this case, the present infinitive is posse (which is based on esse, the present infinitive of sum).
Here are the forms of the present and imperfect subjunctive. Subjunctives are hard to translate in isolation, but the present tense is something like I may be able, you may be able, etc. The imperfect tense can be translated as I might be able, you might be able, etc.
Perfect System (Indicative)
The perfect system includes the perfect, pluperfect, and future perfect tenses of the indicative mood, as well as the perfect and pluperfect tenses of the subjunctive.
Possum is totally regular in the perfect system, both in the indicative and in the subjunctive. You simply add the appropriate endings to the perfect stem, potu-.
(Remember: you find the perfect stem of a Latin verb by removing –ī from the third principal part.)
Here is a conjugation chart showing the perfect indicative of possum:
I was / have been able, I could
we were / have been able, etc.
you were / have been able, you could
you (y’all) were / have been able, etc.
he/she/it was / has been able, etc.
|potuērunt / potuēre|
they were / have been able, etc.
And here is the pluperfect indicative of possum:
I had been able
we had been able
you had been able
you (y’all) had been able
he/she/it had been able
they had been able
And then the future perfect indicative of possum:
I will have been able
we will have been able
you will have been able
you (y’all) will have been able
he/she/it will have been able
they will have been able
Perfect System (Subjunctive)
Finally, let’s look at the perfect and pluperfect subjunctive. Just like with the perfect tenses of the indicative, you add the regular perfect and pluperfect subjunctive endings to the perfect stem (potu-).
It is hard to translate subjunctive forms in isolation, but the perfect means something like I may have been able, you may have been able, etc., while the pluperfect is something like I might have been able, you might have been able, etc.
Infinitives & Participles?
Possum is an irregular verb, as we have seen. But it is also defective. This means that it does not have all of the possible infinitive and participial forms. There are no imperatives, and the gerund and supine are also missing.
Possum has two infinitives.
- posse = to be able (present infinitive)
- potuisse = to have been able (perfect infinitive)
Possum only has one participle: potēns, potentis, a present participle meaning “able, powerful”. While potēns is technically a participle, it is commonly used as an adjective.
How to use the Latin verb possum
As I mentioned up above, possum means “be able to” or “can.” Thus this verb appears extremely frequently with a complementary infinitive.
A complementary infinitive complements or completes the meaning of possum. It tells you what you are able to do, thus finishing the thought.
Consider the following sentence:
Tibi vēritātem dīcere possum. = I can tell you the truth.
In this sentence, dīcere is the complementary infinitive. It explains what I am able to do: tell the truth.
In the following examples, I have put both the form of possum AND the complementary infinitive in bold.
Rēx aurum invenīre nōn potuit. = The king could not find / was not able to find the gold.
Potestisne mē adiuvāre? = Can you (y’all) help me?
Rōmam īre crās poterimus. = We will be able to go to Rome tomorrow.
Māter dīcit sē canem vidēre posse. = Mother says she is able to see the dog.
Nōn potest fierī! = It can’t be / can’t happen!
Sī tē laudāre nōn possem, silērem. = If I were not able to praise you, I would be silent.
Possum can also appear independently without an infinitive (although this is less common). On its own, the verb can mean “have power”, “be powerful,” or “have influence.”
The exact translation depends on the sentence in question, so here are a few examples from ancient Roman texts. Notice how potest can mean “it is possible” in Sentence #3.
#1. Nam, quod ingeniō minus possum, subsidium mihi diligentiā comparāvī. = For, since I am less able / gifted in intellect, I have acquired assistance for myself via diligence. (Cicero, Pro Quinctio 1.4)
#2. Nam in omnī certāmine quī opulentior est, etiam sī accipit iniūriam, tamen, quia plūs potest, facere videtur. = For in every conflict the one who is wealthier, even if he suffers a wrong, seems to inflict it, since he is more powerful. (Sallust, Jugurtha 10.7)
#3. Dignitātem nostram, ut potest in tantā hominum perfidiā et inīquitāte, retinēbimus. = We shall retain our dignity, insofar as it is possible in the midst of such faithlessness and iniquity of men. (Cicero, Letters to Family 1.2.4)
#4. Plūs apud tē pecūniae cupiditās quam iūdiciī metus potuit. = Greed for money had more influence on you than fear of judgment. (Cicero, Against Verres 2.3.131, adapted)
If this independent use of possum confuses you, don’t worry. It is much more common to see possum with an infinitive, so that is what you should focus on at first.
If you see a form of possum on its own, start by trying to translate it as “be able” or “be powerful” and see if that makes sense. With time, you will get used to the different uses!
Derivatives of possum
The Latin verb possum has many descendants in modern Romance languages and in English. I will mention some of these derivatives below, because I find them helpful in remembering the various forms of possum (and its meaning).
Some derivatives have poss– in them; this reminds us of the present system of possum.
Other derivatives have pot-. This reminds us of possum‘s origin in the adjective potis and it can help you remember the T that shows up in the perfect system.
Possum has also given us other words, such as the Spanish poder, poderoso, posible, etc. and French pouvoir, puissante, etc.
I hope that these derivatives will help you remember possum a bit better!
The Latin Verb Possum: Final Thoughts
The verb possum is the 2nd most common verb in the Latin language (coming just after sum). This means that it is very important to understand how it works.
This post has covered how to conjugate and use this extremely frequent verb. Remember the following two facts, and you will be in good shape:
- Forms of possum are built off forms of sum
- Forms of possum usually appear along with a complementary infinitive that explains what you are able to do
How do you feel about possum? I have confidence in you. Tū potes linguam latīnam discere! (You can learn Latin!)
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