Phase Verbs: početi, prestati, nastaviti

A phase verb names the beginning, continuation, or end of an action: početi "begin," prestati "stop," nastaviti "continue," završiti "finish," krenuti "set off / start." They behave like modals syntactically — they govern another verb — but they carry one hard, unbending rule that no modal does: their infinitive complement must be imperfective. You begin, continue, or stop a process, never a finished whole, and Croatian grammar encodes that logic literally. English, with its aspect-neutral "start to read / start reading," hides the rule completely, so this is exactly the place where a confident English speaker produces a sentence that is not merely awkward but ungrammatical. This page covers the verbs, the imperfective rule, and the noun-based alternative built with s/sa + the instrumental.

The phase verbs and their aspect pairs

Each phase verb is itself part of a normal aspect pair, choosing its own aspect like any other verb. Don't confuse the phase verb's own aspect (which behaves normally) with the aspect of the infinitive it governs (which is locked to imperfective).

The first sentence uses perfective početi (a single bounded start); the second uses imperfective počinjati (a repeated, habitual start). That choice follows the ordinary rules of verbal aspect. What stays fixed in both is the complement: učiti, raditi — both imperfective.

The headline rule: the infinitive complement must be imperfective

Here is the rule in one line: after a phase verb, the governed infinitive is always imperfective. There is no choice to weigh and no exception to learn. You begin/continue/stop a process — something with internal duration — and the imperfective is precisely the aspect that views an action as an unfolding process. A perfective infinitive, which packages an action as a completed whole, has no internal stretch to enter into, so it is grammatically blocked.

In each case the perfective partner is impossible: not napisati but pisati, not pročitati but čitati, not pasti but padati. Swapping in the perfective does not soften the meaning — it breaks the sentence.

Why "finish the book" doesn't use a phase verb

Because the completion of an action is so naturally carried by the perfective verb itself, Croatian often expresses English "finish X / get X done" with a plain perfective and no phase verb at all. The phase verb završiti + imperfective focuses on ending the activity; the bare perfective focuses on reaching the result.

For "I got the letter written," the most idiomatic Croatian is simply Napisao sam pismo — the perfective already contains the "done." Reaching for a phase verb here is the English speaker's instinct, not the Croatian one.

The noun alternative: s/sa + instrumental, and the verbal noun

Phase verbs need not govern an infinitive at all. They can take a noun object naming the activity — typically a verbal noun in -nje — introduced by the preposition s / sa (with the instrumental case) for početi "begin" and prestati "stop." This is extremely common, often more natural than the infinitive, especially for habits and named activities.

The choice between the two patterns is partly stylistic, but there is a tendency: the infinitive foregrounds the activity as something done (prestati pušiti, "stop smoking"), while the s + instrumental noun foregrounds it as a named pursuit or programme (prestati s pušenjem, "give up [the habit of] smoking"). Both are correct and idiomatic.

Note that nastaviti and završiti tend to take a direct object (accusative) rather than s + instrumental: nastaviti razgovor ("continue the conversation"), završiti posao ("finish the job").

krenuti: "set off, get going"

Krenuti (perfective; imperfective kretati) is the most motion-flavoured phase verb — "set off, start moving, get going." It often governs an imperfective infinitive like the others, but it equally takes a destination or a u/na + accusative phrase, since its core sense is departure.

A stacked example

Phase verbs combine freely with modals, which sit one level up. The modal takes the phase verb, and the phase verb in turn forces the imperfective:

The modal morati freely governs the phase verb početi; početi then locks the complement to imperfective učiti. Each layer follows its own rule.

Common Mistakes

Key Takeaways

• Phase verbs — početi/počinjati, prestati/prestajati, nastaviti/nastavljati, završiti/završavati, krenuti/kretati — name the begin/continue/end of an action.
• Their governed infinitive is always imperfective: Počeo sam pisati, never *Počeo sam napisati. This is a hard grammatical rule, not a preference.
• The phase verb chooses its own aspect normally; only the complement is locked.
• početi and prestati also take a noun with s/sa + instrumental (početi s radom, prestati s pušenjem); nastaviti and završiti tend to take an accusative object.
• For "finish/get X done," Croatian often skips the phase verb and uses a bare perfective (Pročitat ću knjigu, Napisao sam pismo).