Present Subjunctive of Sum and Possum

The common verbs sum, esse, fuī, futūrus “be” and possum, posse, potuī “be able” are irregular, but their present subjunctives form a tightly connected pair. Learn sim first; every form of possim then becomes pot- plus that form, with the sounds assimilated. This page concentrates on form and parsing. The many clause types that select the subjunctive are treated elsewhere.

Both paradigms are (neutral Classical). Neither verb has a passive: being and being able do not present an action transferred to an object. English often hides mood inside “be,” “may,” “can,” “could,” or an infinitive, so reliable reading must begin with the Latin form rather than the first plausible translation.

For the regular mood vowels and endings that provide the wider pattern, see Present Subjunctive: Formation.

The two paradigms

The present subjunctive of sum uses the stem si-/s- rather than the indicative forms sum, es, est. Its endings still reveal person and number.

The long ī is visible in sīs, sīmus, and sītis, but not in sim, sit, or sint. The same quantities carry into possīs, possīmus, and possītis. Macrons are pedagogical; an ancient manuscript normally does not print them.

In the first sentence, sint is third-person plural because omnēs is plural. In the second, sīmus is first-person plural because the understood subject is “we.” English chooses “may be” for the possible wish and “to be” after “asks”; Latin uses the same morphological present subjunctive in two different constructions. An unattainable present wish would instead normally use the imperfect subjunctive.

How possim grows from sum

The first two principal parts show the relationship: possum historically contains pot- plus sum, and posse contains pot- plus esse. Before s, ts assimilates to ss: pot-sum becomes possum, and pot-sim becomes possim. This is not the regular subjunctive formation of a third-conjugation verb, even though some endings may look familiar.

Possit and possint govern complementary present infinitives, here venīre and intrāre. The finite form carries person, number, tense, and mood; the infinitive names the action that is possible.

Do not add an English “to” construction mechanically. Latin possum takes a complementary infinitive without ut: venīre possum “I can come.” An ut in the sentence belongs to some larger clause, as in cūrā ut ... possint “see to it that ... can.”

What “present” means here

“Present subjunctive” is a morphological label. In a primary sequence it usually represents an action simultaneous with or later than the leading verb, but its English equivalent depends on the construction.

In nē serō sit, English naturally says “may be.” In the purpose clause, possīmus is simply “we can.” In the potential question, sit becomes “could be.” None of those English auxiliaries is part of the Latin form itself.

The present subjunctive is built from the present system, not from the perfect stem fu- or potu-. Those perfect stems form fuerim and potuerim, which normally present being or ability as anterior or completed. Compare:

The contrast is not English “can” versus “may.” It is Latin present-system possīs versus perfect-system potuerīs.

A form-first parsing routine

When you meet sītis or possint, do not begin by guessing which English word sounds right.

1. Isolate the ending: -tis marks second-person plural; -nt marks third-person plural.
2. Identify the irregular base: si-/s- belongs to sum; possi-/poss- belongs to possum.
3. Name the morphology: present subjunctive, active in traditional terminology, though neither verb has a passive counterpart.
4. Read the surrounding syntax: an ut purpose clause, indirect question, wish, command, or another construction determines the translation.

Here sit does not mean that the shop's existence is doubtful. It is subjunctive because ubi sit taberna is an indirect question. Mood marks the clause's syntactic status, not the speaker's level of confidence.

The future adverb crās gives possīmus future reference even though it is morphologically present. The complementary infinitive esse remains uninflected; possīmus agrees with the understood “we.”

Agreement and complements

With a predicate noun or adjective, sum links two nominative expressions. With possum, the finite verb agrees with its subject while its complementary infinitive does not.

In comes sīs, tū and comes are nominative. In the second sentence, plural discipulī controls both sint and possint. Intellegere supplies the content of their ability.

The second example is a possible-condition pattern (neutral Classical). It does not establish a universal translation “may” for possint. Context could instead require “can” or “would be able.”

Productive forms and exceptional-looking forms

The six forms in each table are the productive Classical paradigm. Early Latin sometimes preserves siem, siēs, siet and related forms (archaic/literary); poets may use them for meter. Recognize them in older or poetic texts, but do not substitute them for sim, sīs, sit in ordinary Classical prose.

Compounds of sum mostly carry the same subjunctive base: adsim “I may be present,” absim “I may be absent,” prōsim “I may benefit.” Their prefixes can undergo their own sound or spelling changes. Those lexical compounds do not alter the central sim paradigm.

Common Mistakes

1. Building the form from English “be”

2. Treating possum as a regular third-conjugation verb

3. Using a perfect stem for present ability

4. Making the infinitive agree with the subject

Key Takeaways

The present subjunctive of sum is sim, sīs, sit, sīmus, sītis, sint. Prefixing pot- and applying assimilation produces possim, possīs, possit, possīmus, possītis, possint. Both are present-system forms, both lack a passive, and neither maps to a single English auxiliary. Parse person, number, tense, and mood first; let the clause type determine the translation.