Perfective anterior gerund

The perfective gerund is a non-finite verb form that acts as an adverbial modifier. Important: Gerunds are immutable (неизменяемые) and do not change for gender, number, or case. Perfective gerunds are formed from perfective verbs (глаголы совершенного вида). Note that bi-aspectual verbs (двувидовые глаголы), such as жениться or исследовать, can also form perfective gerunds when used in a perfective context. It is essential for creating sophisticated sentence structures in Russian.

1. Formation:
Unlike imperfective gerunds, which are formed from the present tense stem, perfective gerunds are primarily formed from the infinitive or past tense stem.

• -в: Added to the past tense stem of verbs ending in a vowel. Example: прочитать → прочитав (having read). (Note: -вши can also be used for non-reflexive verbs ending in a vowel, like сделавши, but this variant is highly colloquial).
• -вшись / -шись: Used for reflexive verbs. Use -вшись after vowels (улыбнуться → улыбнувшись) and -шись after consonants (запереться → запершись).
• -я / -а: This is the modern standard for many common consonant-stem verbs, especially verbs of motion. It is added to the simple future tense stem. Examples: уйти (уйд-ут) → уйдя (having left), принести (принес-ут) → принеся (having brought).
• -ши: Also used for some stems ending in a consonant, though less common than -я/-а for many everyday verbs. Example: спасти → спасши (having saved).

Note: While you might encounter forms like заметя or положа in classical literature, they are considered obsolete and incorrect in modern Russian. Some of these archaic forms survive only in fixed idioms, such as положа руку на сердце (honestly / laying one's hand on one's heart), while others, like заметя, are simply archaic and incorrect in modern standard Russian. The modern standard forms are заметив and положив.

2. Usage Rules:

• Sequence and Result: The action of the gerund usually happens before the main verb, but it can also describe an action that occurs immediately after or as a direct result of the main action (e.g., 'Он упал, сломав ногу' - He fell, breaking his leg).
• Identical Action: The gerund can represent the exact same action as the main verb, explaining how the main action was achieved (e.g., 'Он совершил ошибку, согласившись на это' - He made a mistake by agreeing to this).
• Subject Constraint: The subject of the gerund must be the same as the subject of the main verb. Exception: It can be used in impersonal sentences if the main verb is an infinitive (e.g., 'Прочитав статью, полезно сделать выводы' - Having read the article, it is useful to draw conclusions).
• Punctuation: Gerunds and gerundial phrases (деепричастные обороты) must almost always be set off by commas, regardless of their position in the sentence. Exceptions include fixed phraseological expressions (idioms), which are never set off by commas (e.g., работать спустя рукава, бежать сломя голову). Additionally, single perfective gerunds denoting a physical state or posture (answering 'how?') lose their verbal nature and are not set off by commas (e.g., 'Он сидел ссутулившись' - He sat hunched over).
• Negation: The negative particle не is generally written separately from gerunds (e.g., не прочитав - not having read). However, it is written together if the verb cannot be used without 'не' (e.g., невзлюбив - having taken a dislike to) or when using the prefix недо- (e.g., недосолив - having undersalted).
• Register: This form is primarily used in written Russian. In speech, subordinate clauses with когда are more common.