A Doll’s House

https://www.gutenberg.org/files/2542/2542-h/2542-h.htmA Doll’s HouseWhat is the significance of the nicknames Torvald has for Nora? What is the effect of the use of titles and of last names alone (Doctor versus Rank, Mrs. Linde versus Kristine, Nils as opposed to Krogstad)? How do these names reflect the relationships between characters?