Nomen: ______Classis: ______Review Notes: “possum” and the Complementary Infinitive – Aug 30/31

Principal parts of the verb “possum”: possum, posse, potui, ----- to be able to, can

Possum is a compound of the verb sum. It is essentially the prefix pot added to the irregular verb sum. However, the letter t in the prefix pot becomes s in front of all forms of sum beginning with the letter s.

Let’s look at the forms of the verb “possum” below and their translations:

Present Tense Singular Plural

Latin English Translation Latin English Translation

1. possum I can, I am able possumus We can, we are able

2. potes You can, you are able potestis Y’all can, are able

3. potest He/she/it can, is able possunt They can, are able

Imperfect Tense Singular Plural

Latin English Translation Latin English Translation

1.poteram I could, was able poteramus We could, were able

2.poteras You could, were able poteratis Y’all could, were able

3.poterat He/she/it could, was able poterant They could, were able

Future Tense Singular Plural

Latin English Translation Latin English Translation

1.potero I will be able poterimus We will be able

2.poteris You will be able poteritis Y’all will be able

3.poterit He/she/it will be able poterunt They will be able

So what about the perfect, pluperfect, and future perfect forms of the verb “possum”? These tenses are regular, meaning possum follows the normal rules. Let’s look at them. Start by rewriting your principal parts of the verb:

Possum, posse, potui, ------to be able to, can

Just like all other verbs, switch to the 3rd principal part when you want to work in the perfect, pluperfect, and future perfect tenses.

Perfect Tense Singular Plural

Latin English Translation Latin English Translation

1. potui I could, was able potuimus We could, were able

2. potuisti You could, were able potuistis Y’all could, were able

3. potuit He/she/it could, was able potuerunt They could, were able

Pluperfect Tense Singular Plural

Latin English Translation Latin English Translation

1. potueram I had been able potueramus We had been able

2. potueras You had been able potueratis Y’all had been able

3. potuerat He/she/it had been able potuerant They had been able

Future Perfect Tense Singular Plural

Latin English Translation Latin English Translation

1. potuero I will have been able potuerimus We will have been able

2. potueris You will have been able potueritis Y’all will have been able

3. potuerit He/she/it will have potuerint They will have been been able able

Finally, one last note: like the verb sum, possum can only be active voice. There’s no such thing as a passive form of the verb “to be able to”.

Complementary Infinitive

Possum is not a complete verb on its own. It needs an infinitive to complete its meaning. The infinitive is the 2nd principle part of a verb. When an infinitive is used with possum, it is called a complementary infinitive.

Like conjugated verbs, complementary infinitives can have direct objects, which as always are in the accusative case. They may also have prepositional phrases, and anything else conjugated verbs have (except for a subject!).

Ex: Paucos homines in insulā cernere poteram.

I was able to discern few people on the island.  “Few people” is the direct object of cernere, not poteram.

The verb debeo, debere, debui, debitus, when it means “ought”, also uses a complementary infinitive.