я + -ю/-у

In Russian, the verb ending changes based on who is performing the action. For the first-person singular (I), the endings are usually -ю or -у. These endings are exactly the same regardless of whether the verb belongs to the 1st or 2nd conjugation.

1. Choosing the Ending:

• -ю is used after vowels (e.g., читать → я читаю) and to indicate that the preceding consonant is soft (e.g., in говорить → я говорю, the 'ю' tells the reader to pronounce the 'р' as soft or palatalized).
• -у is used after hard consonants (e.g., идти → я иду, жить → я живу) or when required by the spelling rules (never write 'ю' after ж, ч, ш, щ, г, к, х, ц in verb endings). For example: пишу, вижу.

2. Consonant Mutations and Stress:
Many verbs change their stem consonant when conjugated. Common mutations include: д/з → ж, т → ч (and ст → щ), с → ш, and the addition of л to labial consonants б, в, м, п, ф. In the first conjugation, this change typically persists through all conjugated forms (e.g., писать → я пишу, ты пишешь). However, for velar stems (verbs ending in -чь, like мочь or печь), the 'я' and 'они' forms use the hard consonant (я пеку, они пекут), while the other forms mutate (ты печёшь). In the second conjugation, the consonant changes only in the 'я' form (e.g., любить → я люблю, but ты любишь). Additionally, the 'я' form often has a different stress pattern than the rest of the conjugation. For many second conjugation verbs, the stress falls on the ending for 'я' but shifts backward to the stem for other pronouns (though some, like говорить, keep the stress on the ending throughout).

3. Special Suffix Mutations:
Some common verb groups have specific changes in the present tense:

• Verbs with the suffix -ова- or -ева- change this suffix to -у- or -ю- before adding the ending (e.g., рисовать → я рисую, танцевать → я танцую). Note that if the verb is formed with the suffix -ва- added to a root ending in -е, the verb conjugates regularly (e.g., надевать → я надеваю). Verbs like зевать and здороваться are also regular (я зеваю, я здороваюсь) because the 'ев' or 'ов' is part of the root (зев-, здоров-), not a suffix.
• Verbs derived from the roots -да- (give), -ста- (stand), and -зна- (know) — such as давать, вставать, and узнавать — drop the -ва- suffix (e.g., давать → я даю, вставать → я встаю, узнавать → я узнаю). This rule does not apply to regular verbs like плавать (я плаваю).

4. Reflexive Verbs:
Because regular 'я' endings (-ю and -у) are vowels, the reflexive suffix for the first-person singular is -сь. For example: я учусь (I study), я одеваюсь (I dress myself).

5. Usage and Tense:
These endings apply to both the present and simple future tenses, depending on the verb's aspect. For imperfective verbs, it creates the present tense (я читаю means both 'I read' and 'I am reading'). For perfective verbs, it creates the simple future tense (я прочитаю means 'I will read'). Additionally, while native speakers often include the pronoun я, the verb ending itself is so distinct that the pronoun is sometimes omitted in casual speech.

6. Exceptions and Special Cases:

• Irregular verbs: есть (to eat) becomes я ем, and дать (to give) becomes я дам. This irregularity also applies to all of their prefixed derivatives (e.g., съесть → я съем, продать → я продам).
• Unpredictable stem changes: Some high-frequency verbs have unpredictable stem changes in the 'я' form that must be memorized (e.g., ехать → я еду, брать → я беру, искать → я ищу).
• The verb 'быть' (to be): In modern Russian, the present tense form ('I am') is omitted entirely. However, its future tense takes a standard ending: я буду.
• Defective verbs: Some verbs, like победить (to win/defeat), убедить (to convince), and очутиться (to find oneself), completely lack a first-person singular form due to historical phonetic awkwardness (words like 'побежу' do not exist). To express these ideas, you must use a workaround, such as я смогу победить (I will be able to win) or я одержу победу (I will achieve victory).