Którym

Którym is a form of the Polish relative pronoun który. It is used for masculine singular antecedents and appears in the instrumental and locative cases, often after prepositions, to introduce a relative clause. In other genders and numbers, other forms of który are used (for example, który, która, które), but кои forms of interest here are those that yield the instrumental/locative sense in phrases like w którym or z którym.

Grammtically, który behaves like a declined demonstrative pronoun, and który’s relative form is chosen to agree with the gender, number, and case of its antecedent. The instrumental and locative forms of masculine singular are identical in this word, both realized as którym, so a clause such as w którym mieszkam can mean “in which I live.” Other case forms for masculine singular exist (nominalny który, genitive którego, dative któremu, accusative którego), and feminine and neuter forms follow their own declensions (for example która/której/której/którą/którym/której for feminine, które/którego/któremu/które/którym/którym for neuter).

Usage notes include that który/którymi forms are standard in written Polish and in formal speech, but in everyday conversation their relative clauses may be shortened or rephrased with other constructions. The word is also used in interrogative contexts as a base form of which in questions like Którym z tych rozwiązań chcesz się posłużyć? Although primarily a relative pronoun, który is etymologically connected to the broader Slavic system of "which/that" pronouns, sharing a common root with related forms in neighboring languages.

See also: który, która, które, któryś, relative clauses in Polish.