Katya (unidentified, subject of Pleshcheyev's inquiry)

A young woman, unidentified by surname in this letter, whose relationship with an unnamed older professor had evidently become the subject of gossip; Pleshcheyev had apparently asked Chekhov about it, and Chekhov mounts a pointed defense of her, arguing that platonic affection between people is real and that assuming otherwise -- imagining her in love with a "half-dead old man" -- would itself be a "sexual perversion" of only clinical, psychiatric interest. Not identified with any other Katya in this corpus (a common name across multiple unrelated Chekhov works and letters); left unresolved per lack of surname or other disambiguating detail in the source.