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Aspect Pairs Tool – Overview and Methodology

Overview

The category of grammatical aspect is one of those topics that native speakers and teachers of Slavic languages (including Czech) are often reluctant to discuss, and that students frequently dread learning. This is undoubtedly due to its extreme complexity, unpredictability, and the inherent difficulty of explaining it in a clear, visual way.

While a dedicated e-book 1 and several websites 2 are available for Czech, a comprehensive, user-friendly tool for quickly looking up aspect pairs has been missing until now.

Aspect Pairs Tool in This Guide

Launched on June 1, 2026, this guide now includes a continuously growing database of aspect pairs that can be searched quickly and that provides additional grammatical information.

Try it below, or visit the dedicated page for additional features, including an error-reporting form and information about the size of the database.

Methodology

When developing this tool, we followed these rules:

  1. The imperfective lemma is treated as the primary word form. The perfective lemma is secondary, as it is usually derived from the imperfective form.
  2. To form an aspect pair, the imperfective and perfective verbs must have the same meaning. If the meaning is not the same, the pair is not created.
  3. If there is a relationship between multiple aspect pairs, the Related link points primarily to the imperfective lemma.
  4. Reflexive verbs (i.e. verbs with si or se) have their individual entry only if they are reflexive tantum (i.e. reflexive only). For example, the verb smát se (to laugh) does exist only as reflexive and is mentioned in the database exactly like this. On the other hand, a word such as zlepšovat (to improve) exists as both zlepšovat and zlepšovat se and only the non-reflexive form has its own entry.
  5. Entries contain several grammatical details, namely the infinitive (the lemma), aspect category, conjugation category, 1st and 2nd person singular form, and links to Příručka, Slovník Seznam, and Nechybujte.
  6. Some entries contain examples in both Czech and English. Although the initial goal was to provide examples for every entry, this proved to be impractical because of the time required. Furthermore, the linked external resources already provide a sufficient number of examples, and reproducing them here would largely duplicate existing content. As a result, some entries still contain legacy examples, but the majority do not.
  7. Colloquial and slang words are rarely included.
  8. A vast number of Czech verbs have iterative forms (e.g., pracovat → pracovávat, meaning to work → to work habitually/repeatedly). These are omitted from this guide because they are inherently imperfective and do not form new aspect pairs.
  9. This tool is designed to be extendable. It is actively maintained, and users can submit reports about errors they find and suggest missing words for inclusion.

Statistics

See how the number of words in the database has grown over time:

Date Words
01/2026 0
05/2026 3400
06/2026 3575
04.06.2026 3636
05.06.2026 3655
06.06.2026 3882
15.06.2026 4139
16.06.2026 4188
21.06.2026 4426
29.06.2026 4521
10.07.2026 4693
27.07.2026 4836
28.07.2026 4867
30.07.2026 4945
14.09.2026 5152
19.10.2026 5230

Acknowledgment

This tool would not have been launched without the valuable contribution of a member of Czech Language Guide, Terezie Királyiová, to whom we extend our sincere thanks.

  1. Slovník českých vidových dvojic pro cizince (B1-B2). ↩

  2. See Grammatical aspect - Sources in this guide. ↩