Verb aspect expresses how an action extends over time. English has four verb aspects: simple, progressive, perfect and perfect progressive, but Ukrainian doesn’t have these. We have two other aspects: imperfective and perfective. The imperfective describes the process (an uncompleted action) focusing on action, while the perfective shows the result of an action (a completed action).

Most Ukrainian verbs come in imperfective and perfective pairs, but not all. The perfective form of the verb can be formed with the help of:

1. prefixes: “з-, с-, зі-, в-, за-, на-, по-, про-, при-, ви-“:
   йти – прийти́ (to come),
   писа́ти – написа́ти (to write),
   чита́ти – прочита́ти (to read);
2. suffixes: “–а-, -ува-, -ва-“:
   допомага́ти – допомогти́ (to help),
   зігріва́ти – зігрі́ти (to warm);
3. sounds alternation in the stem:
   сиді́ти- сі́сти (to seat),
   збира́ти – зібра́ти (to gather);
4. stress change:
   розріза́ти – розрі́зати (to cut),
   склика́ти – скли́кати (to convene);
5. different words:
   лови́ти – пійма́ти (to catch),
   бра́ти – взя́ти (to take))

Unfortunately there are no way of knowing when to use any of the methods listed above.

Some verbs have only imperfective or perfective form.