The Infinitive (-ти / -ть)

The infinitive (неозна́чена фо́рма дієсло́ва, or simply інфініти́в) is the "name" of a verb — the form you find in a dictionary, the form you learn first, and the form that does no work of its own until another verb or construction picks it up. In Ukrainian it almost always ends in -ти: чита́ти ("to read"), говори́ти ("to speak"), роби́ти ("to do"), бу́ти ("to be"). This page covers its spelling (and the one variant ending you should recognise but rarely use), its jobs in a sentence, and the single feature that has no English parallel: the infinitive carries aspect, so "to read" is two different infinitives depending on whether you mean the process or its completion.

The standard ending is -ти

In standard Ukrainian, the infinitive ends in -ти. This is non-negotiable for writing and neutral speech.

The -ть variant: recognise it, don't default to it

You will hear and read -ть instead of -ти: носи́ть for носи́ти, спать for спа́ти, гуля́ть for гуля́ти. This is (informal) in everyday speech and especially (literary / poetic) in song lyrics and folk verse, where it shortens a line to fit the metre. It is not the Russian default — Russian uses -ть as its standard infinitive ending, whereas in Ukrainian -ть is a marked, optional contraction of -ти. Treat -ти as your only spelling and -ть as something you simply understand when you meet it.

The -ти → -кти / -гти and -чи irregulars

A handful of very common verbs whose stem ends in a velar к or г don't show a clean -ти. They surface as -кти, -гти, or -чи.

There's no productive rule generating new verbs like these — the set is closed and small. Just learn могти́, бі́гти, пекти́, берегти́, лягти́ as fixed shapes; the present tense of several of them shows a г → ж change (можу́, біжу́, печу́), covered under present-stem consonant changes.

What the infinitive does in a sentence

The infinitive rarely stands alone. Its main job is to be the second verb after another verb or expression that selects it.

1. After modal and "wanting" verbs

2. After phase verbs (begin, finish, continue)

3. In impersonal necessity, advice, and prohibitions

The infinitive is the backbone of impersonal sentences with тре́ба ("need to"), мо́жна ("may, it's allowed"), не мо́жна / не + infinitive ("must not"), and questions like Що роби́ти? ("What to do?").

4. Building both futures

The infinitive is the raw material for both Ukrainian futures from an imperfective verb. The analytic future is бу́ду + infinitive; the synthetic future fuses -му onto the infinitive itself.

See the analytic future and synthetic future pages for the full mechanics.

The big one: the infinitive carries aspect

This is where Ukrainian diverges sharply from English. English has one infinitive, "to read," and context alone tells you whether you mean reading-as-an-activity or reading-something-to-the-end. Ukrainian splits that single English form into two infinitives — an imperfective one and a perfective one — and you must choose.

• чита́ти (imperfective) — to read, as a process or habit, no endpoint implied
• прочита́ти (perfective) — to read through, to finish reading, a completed act

So "I want to read a book" is genuinely two different sentences in Ukrainian, and they mean different things:

The choice English makes with no inflection at all — just context — Ukrainian forces you to make in the verb's very shape. Getting comfortable with it is the gateway to the whole aspect system, the single most important feature of the Ukrainian verb.

Reflexive infinitives end in -тися (and contracted -ться)

Reflexive verbs add the particle -ся after the infinitive ending: умива́тися ("to wash oneself"), смія́тися ("to laugh"), подо́батися ("to please / to be liked"). In standard spelling the full ending is -тися; the contracted -ться appears in the conjugated present (сміє́ться) and in the colloquial/poetic infinitive.

Source-language comparison

For an English speaker, two things are new. First, English marks the infinitive with a separate word, "to" ("to read"), while Ukrainian marks it with the ending -ти — there is no Ukrainian word for "to." Don't look for one. Second, and far more important, English has a single infinitive where Ukrainian has an aspect pair; "to read" must be resolved into чита́ти or прочита́ти. Until you internalise aspect, default to the imperfective (-ти base form) when no result is implied, and reach for the perfective when you mean "get it done."

For a Russian speaker, the trap is the ending: Russian's standard infinitive is -ть (читать), which in Ukrainian is the colloquial variant. Standard Ukrainian is -ти (чита́ти). Retrain your fingers and your ear to -ти; the velar-stem verbs are also -ти / -чи (могти́, текти́), not Russian -чь.

Common Mistakes

Key Takeaways

• The infinitive (неозна́чена фо́рма) is the dictionary form, ending in standard -ти (чита́ти, бу́ти); -ть is a colloquial/poetic variant to recognise, not to use.
• A closed set of velar-stem verbs ends in -кти / -гти / -чи (могти́, пекти́, берегти́, бі́гти, текти́).
• The infinitive is the second verb after modals (хо́чу чита́ти), phase verbs (поча́в працюва́ти), in impersonal necessity (тре́ба йти), and builds both futures (бу́ду чита́ти / чита́тиму).
• It carries aspect: чита́ти (process) vs прочита́ти (read through) — a distinction English makes with context alone.
• Reflexive infinitives end in -тися (смія́тися, боя́тися).
• Ukrainian has no word for "to" before the infinitive — the ending does the job.