What is the grammatical function of the particle 'by' in Polish subordinate clauses, and in what type of clauses is it most commonly found?

The grammatical function of the particle 'by' in Polish subordinate clauses is to indicate the subjunctive or conditional mood, expressing hypothetical situations, wishes, or possibilities. It doesn't have a direct translation but signals that the action in the subordinate clause is not factual or certain. 'By' is most commonly found in conditional clauses (expressing what *would happen), purpose clauses (expressing the intention or aim of an action), and wish clauses (expressing a desire). For example, in the sentence 'Chcę, żebyś to zrobił' (I want you to do it), 'żebyś' (żeby + 'byś') introduces a purpose clause, expressing the desired outcome. In 'Gdyby padało, zostałbym w domu' (If it were raining, I would stay home), 'Gdyby' (gdy + 'by') introduces a conditional clause, expressing a hypothetical condition. 'By' is crucial for forming these moods and expressing nuances of meaning beyond simple statements of fact in subordinate clauses.