-л/-ла/-ло

The Russian past tense is formed using the infinitive stem. Both imperfective and perfective verbs (e.g., читал vs. прочитал) use these exact same formation rules. Usually, you remove the -ть and add the suffix -л followed by a gender marker.

1. Basic Endings:

• Masculine: -л (no additional vowel / zero ending). Example: Он читал.
• Feminine: -ла. Example: Она читала.
• Neuter: -ло. Example: Оно стояло.
• Plural: -ли. Example: Они читали.

2. Agreement with Pronouns:
Unlike the present tense, the past tense does not conjugate for person (1st, 2nd, 3rd). This means я (I), ты (you), and он (he) all use the exact same verb form if the subject is masculine. Because the past tense agrees with gender, the verb for 'я' and 'ты' depends on the biological sex of the person speaking or being addressed. A man says 'Я работал', while a woman says 'Я работала'. Furthermore, the formal or plural вы (you) always takes the plural ending -ли, even when addressing a single person (e.g., Вы работали).

3. Special Cases:

• Consonant Stems: Verbs ending in -ти (e.g., нести) drop the -л in the masculine form (Он нёс), but it returns in the other forms (Она несла). Note that for verbs ending in -ти whose present/future stem ends in д or т (e.g., вести, плести), the д or т is dropped in all past tense forms, and the masculine form keeps the -л (e.g., вести -> вёл, плести -> плёл). Notice the vowel mutation from 'е' to 'ё' in these masculine forms. An exception is the highly common verb расти (to grow), which drops the т in all past tense forms and drops the -л in the masculine form, and also changes the vowel 'а' to 'о' (Он рос, Она росла). Another major exception is the highly common verb идти (to go), which has completely irregular past tense forms (see Irregular Verbs below). Similarly, verbs ending in -зть (e.g., лезть, грызть) drop the -л in the masculine form (Он лез, Он грыз), but it returns in the other forms (Она лезла, Она грызла). Verbs ending in -чь (e.g., печь, мочь) have past tense stems ending in г or к (мог-, пек-). They drop the -л in the masculine form (Он мог, Он пёк), but it returns in the other forms (Она могла, Она пекла). Notice the vowel mutation from 'е' to 'ё' in the masculine form (пёк), which reverts to 'е' in other forms (пекла).
• Verbs in -нуть: Many verbs ending in -нуть (e.g., привыкнуть, исчезнуть) drop the -ну- suffix in all past tense forms, and additionally drop the -л in the masculine form (Он привык, Она привыкла). However, action verbs ending in -нуть (like прыгнуть) keep the regular endings (прыгнул, прыгнула).
• Verbs in -ереть: Verbs ending in -ереть (e.g., умереть, запереть) drop the final -е- in all past tense forms and drop the -л in the masculine form (Он умер, Она умерла).
• Irregular Verbs: The highly common verb идти (to go) has completely irregular past tense forms: шёл (masculine), шла (feminine), шло (neuter), шли (plural). Prefixed verbs based on идти inherit these forms (e.g., подошёл, ушла). Another important irregular verb is есть (to eat), which drops its infinitive stem entirely to become ел (masculine), ела (feminine), ело (neuter), and ели (plural).
• Reflexive Verbs: The reflexive suffix is added after the gender ending. Use -ся after consonants (одевался) and -сь after vowels (одевалась, одевалось, одевались).
• Stress Shifts: Some common verbs shift stress to the final -а in the feminine form (была, дала), while others stay on the stem. Additionally, with negation in the past tense, the stress shifts to 'не' for masculine, neuter, and plural forms (не был, не было, не были) only for a small group of highly common monosyllabic verbs (like быть, дать, жить, пить), but remains on the verb for the feminine form (не была).