Past tense with být auxiliary

Everyday Czech typically uses one main past tense for all past actions, whether they were completed, ongoing, or happened before another past event. The distinction between completed and ongoing actions is handled by aspectual verb pairs, not by changing the tense.

How to form it:
Combine the past participle (often called the l-participle) with the present tense of the auxiliary verb být. To form the regular l-participle for verbs ending in a vowel before the -t, drop the -t from the infinitive and add -l (e.g., dělat -> dělal). Verbs ending in a consonant before the -t (like péct -> pekl) or in -nout (like tisknout -> tiskl) have different stem changes or drop the -nu-. Note that some common verbs have irregular past participles (e.g., jít -> šel/šla, mít -> měl, číst -> četl). The l-participle acts like an adjective and must agree with the subject in gender and number.

• 1st person: dělal jsem (I did - masc.), dělala jsem (fem.)
• 2nd person: dělal jsi (you did - masc.), dělala jsi (fem.)
• 3rd person: dělal (he did), dělala (she did), dělalo (it did) - No auxiliary!
• 1st pl: dělali / dělaly jsme (we did)
• 2nd pl: dělali / dělaly jste (you did)
• 3rd pl: dělali / dělaly / dělala (they did) - No auxiliary!

For all plural persons (1st, 2nd, and 3rd), the past-tense plural gender endings depend on the subject: -i for masculine animate, -y for feminine and masculine inanimate, and -a for neuter (e.g., a group of women would say dělaly jsme).

Formal Singular (Vykání):
When addressing one person formally using vy, you use a split agreement: the plural auxiliary jste is used, but the past participle remains singular to match the person's actual gender (e.g., Co jste dělal? to a man, Co jste dělala? to a woman).

Reflexive Verbs:
When using the 2nd-person singular auxiliary jsi with reflexive verbs, it must fuse with the reflexive pronouns se and si to form ses and sis (e.g., smál ses - you laughed, koupil sis - you bought for yourself). In the 3rd person, since the auxiliary is dropped, the reflexive pronoun simply stands alone in the second position (e.g., Smál se - he laughed, NOT Je se smál).

The Clitic Rule:
The auxiliary verbs (jsem, jsi, jsme, jste) are second-position clitics. They cannot start a sentence and must be placed immediately after the first stressed unit of the clause. They do not have to stay next to the main verb. When auxiliaries share the second position with other clitics like the reflexive se or si, the auxiliary always comes first (e.g., Učili jsme se, NEVER Učili se jsme).

Negation:
To make the past tense negative, attach the negative prefix ne- to the l-participle, never to the auxiliary verb (e.g., Nedělal jsem - I didn't do). Do not negate the auxiliary (e.g., Nejsem dělal is incorrect).

Pro-drop language:
Because the auxiliary and the participle ending already show who is doing the action, subject pronouns (já, ty, my) are usually dropped unless you want to add strong emphasis.

Spoken Czech:
In everyday spoken Czech, jsem is often pronounced as sem, and jsi is frequently attached directly to the verb as an -s suffix (e.g., dělals instead of dělal jsi). Additionally, jsme and jste are almost universally pronounced as sme and ste. Furthermore, in Common Czech, the strict 3rd-person plural endings often collapse, and neuter nouns frequently take the -y ending instead of -a (e.g., auta jely instead of the standard auta jela).