-ся (у дієприслівнику)

The reflexive adverbial participle is a standard feature of educated Ukrainian speech and writing. It allows you to combine two actions into one sentence without using a conjunction like 'and' or 'while'. As an invariable form, it does not change for gender, number, or case, distinguishing it from adjectival participles.

1. Core Questions:
To identify or form these participles, Ukrainian grammar uses two specific questions:

• що роблячи? (what doing?) — for imperfective actions happening simultaneously with the main verb.
• що зробивши? (what having done?) — for perfective actions completed before the main verb.

2. Formation:

• Imperfective (Simultaneous): Take the 3rd person plural (they) of the present tense, remove the entire reflexive ending (-ться), and add the adverbial suffix -чись to the remaining stem. Example: вмиваються (they wash themselves) → remove -ться → add -чись = вмиваючись (while washing oneself).
• Perfective (Sequential): Take the infinitive stem and add -вши plus the reflexive particle -сь for vowel stems (e.g., повернутися → повернувшись, having returned). For stems ending in a consonant, form it from the masculine past tense stem and add -шись. This is crucial because root vowels often alternate (e.g., запектися → past tense запікся → запікшись, having baked/crusted over).
• Note on Vowels: In all Ukrainian adverbial participles, the vowel immediately preceding the reflexive suffix is always the letter и (e.g., -чись, -шись).

3. The -ся vs -сь Rule:
In modern Ukrainian, the reflexive suffix typically becomes -сь in standard prose when it follows a vowel. Since all adverbial participle endings (-чи, -ши) end in a vowel, -сь is the modern literary standard. However, you may still encounter the -ся form in poetry to maintain meter or in older literary texts.

4. Negation:
When using negation, the particle не is written separately (e.g., не вмиваючись), unless the verb cannot exist without не.

5. Punctuation:
In Ukrainian, a participial phrase is usually set off by commas regardless of its position. However, commas are omitted in three specific cases: if a single participle acts as a pure adverb of manner following the verb (e.g., Він сидів задумавшись, He sat lost in thought); if the participle is part of a phraseological unit or idiom (e.g., працювати не покладаючи рук, to work tirelessly); or if the participle is linked to another adverbial by a coordinating conjunction (e.g., Він говорив швидко і не зупиняючись).

6. The Same-Subject Rule:
Crucially, the person performing the main action must be the same person performing the action of the participle. This shared-subject rule applies to all adverbial participles. If the subjects are different, you must use a subordinate clause with якщо or коли instead.