Aspect after Modal Verbs

After моћи “can,” морати “must,” смети “be allowed/dare,” хтети “want/will,” and modal требати “should,” aspect belongs to the complement event. The modal says whether that event is possible, required, permitted, intended, or advisable; the imperfective presents its activity or recurrence, while the perfective presents a bounded outcome.

No modal mechanically selects one aspect. A perfective complement is not automatically future, and an imperfective complement is not automatically more polite. The choice depends on what the ability, obligation, or intention is directed toward.

The core contrast: activity versus attained result

Use one lexical situation to see the distinction. With писати, the modal concerns engaging in writing; with написати, it concerns producing a completed text.

The first speaker offers time for the activity; no endpoint is promised. The second claims ability to deliver the bounded result by a deadline.

English have to read can express either obligation. Serbian forces a useful decision: required effort versus required completion.

Моћи: ability, opportunity, and feasibility

Моћи can describe general ability, a temporary opportunity, or feasibility. General skill often favors an imperfective activity; success in one bounded task often favors perfective.

This describes a standing ability to perform an activity. By contrast:

Here the deadline and definite object make completed processing relevant. The sentence asserts feasibility, not actual completion.

Under negation, aspect distinguishes lack of access to the activity from inability to attain the result.

The second example uses perfective прочитам for one failed achievement. See ability and permission for the forms and wider meanings of моћи.

Морати and требати: obligation versus recommendation

Морати imposes necessity. Aspect identifies whether the necessary content is sustained/repeated conduct or a bounded achievement.

Imperfective провераваш describes a continuing work rule. Perfective провериш requires one completed check before the next action.

Modal требати usually appears impersonally in standard Serbian: треба да + present, with past требало је да and conditional требало би да. The complement's aspect still carries the activity/result contrast.

The habitual frame selects imperfective вежбаш; the single counted repetition selects perfective поновиш.

Personal modal forms such as требам да идем occur in parts of the BCMS area and in some speakers' Serbian usage (regional/informal), but neutral standard Serbian normally uses треба да идем for “I should go.” This is separate from lexical требати with a dative experiencer: Треба ми помоћ “I need help.”

Смети: permission and prohibition

With positive смети, imperfective often grants permission for an activity, while perfective grants permission to perform one bounded act.

The first is a general permission. The second licenses one delimited object. In real usage either aspect can appear when context supplies both an activity and a natural boundary; the contrast is viewpoint, not a rigid countability test.

Negative не смети makes the contrast especially clear:

Imperfective отвараш expresses a general prohibition against the activity. Perfective отвориш warns against one prohibited completion. Negative contexts influence aspect strongly, but do not impose a universal “negation takes imperfective” rule.

Хтети: willingness, intention, and refusal

As a full modal verb, хтети + да-clause expresses desire, intention, or willingness. Imperfective focuses on doing the activity; perfective focuses on obtaining the result.

The first intention concerns participation in a conversation. The second is result-oriented and may fail even if a conversation occurs.

Negative нећу да often expresses refusal rather than simple futurity.

This is a general policy, so imperfective потписујем is natural. In a single situation, Нећу да потпишем овај уговор means “I will not/refuse to sign this contract,” with perfective focus on the withheld result. For the auxiliary use of ћу in Future I, see the dedicated future pages; it should not be conflated with every full-verb use of хтети.

Infinitive and да + present

Both the infinitive and да + present are standard Serbian complements with modals. Everyday Serbian frequently uses да + present, while infinitives remain ordinary, especially in compact constructions. Neither form automatically determines aspect.

Both use perfective пошаљем / послати and promise the same bounded possibility. The syntax changes clitic placement: да ти пошаљем places dative ти immediately after да; могу ти послати places it after the finite modal.

The first infinitive is imperfective because of редовно; the second да complement is perfective because one completed check is required. For the broader syntax, consult да versus the infinitive.

This page deliberately excludes почети, наставити, престати “begin, continue, stop.” Those are phase predicates and are treated under phase verbs; their complement restrictions arise from a different semantic relationship.

Context can make only one choice natural

The first question asks about an ongoing/repeated responsibility, so преводиш is imperfective. The reply limits today's capacity to one completed item, so преведем is perfective. Reversing the forms would change the practical offer, not merely its style.

Common Mistakes

Assuming every modal requires imperfective

Treating perfective after a modal as already completed

Misplacing clitics in a да complement

Practice

Task 1: What satisfies the modal?

Choose читати / прочитати, проверавати / проверити, or слати / послати after the supplied modal. For each answer, state whether the modal targets activity, a standing rule, repetition, or one attained result: морам ... до пет, смем ... овде, могу ... сваког дана, треба ... пре састанка.

Task 2: Change syntax without changing aspect

Rewrite Могу да ти га пошаљем сутра with an infinitive, and rewrite Морамо их редовно проверавати with да + present. Keep clitics in natural order and explain why the aspect stays the same.

Key Takeaways

• The modal supplies possibility, necessity, permission, intention, or advice; aspect shapes its complement event.
• Imperfective normally targets activity, habit, or repetition; perfective targets a bounded result.
• Negation and pragmatics influence aspect, but no modal imposes one member mechanically.
• Both the infinitive and да + present are standard; syntax and clitic placement change independently of aspect.