Realism and naturalism are two distinct movements in theatre that emerged during the 19th century and continue to influence theatre today. Realism in theatre is characterised by an attempt to depict real life and society as it is, without idealisation or romanticisation. The goal of realism is to create a sense of verisimilitude, or the appearance of reality, through the use of detailed characterisations, naturalistic dialogue, and a focus on everyday events. Examples of plays that are considered representative of realism include "A Doll's House" by Henrik Ibsen and "The Cherry Orchard" by Anton Chekhov. David Mamet, Playwright and Director states that "Theatre, in the 19th century, became the laboratory of realism, the place where the new ideas about the nature of reality were tested and refined."
On the other hand, naturalism is an extension of realism that emphasises the scientific observation of human behaviour and the natural world. Naturalistic plays often depict characters who are determined by their environment, biology, and social conditions. The focus is on the objective reality of the characters, rather than their subjective experiences. The goal of naturalism is to depict characters as determined by the laws of nature, rather than by free will. Examples of plays that are considered representative of naturalism include "Miss Julie" by August Strindberg and "The Lower Depths" by Maxim Gorky. George Pierce Baker, theatre professor, states that "Naturalism is the imitation of nature. It is not the same as realism, which is the imitation of nature as it appears to the average person." Encyclopaedia Britannica defines naturalism as "a mode of writing that seeks to describe human behaviour and surroundings or human nature with as much scientific accuracy as possible. It is a literary movement that developed in the late 19th and early 20th centuries in literature, film, theater, and art."
It's important to note that different authors and theatre experts may have different views on the definition of these movements and their characteristics, so it's always a good idea to cross-reference and consult multiple sources when studying theatre.
In summary, realism and naturalism are two distinct movements in theatre that share some similarities, but the main difference is that realism is focused on the appearance of reality, and naturalism is focused on the scientific study of human behaviour and the natural world. Realism in theatre is characterised by an attempt to depict real life and society as it is, without idealisation or romanticisation and naturalism is an extension of realism that emphasises the scientific observation of human behaviour and the natural world. Both of these movements have had a significant influence on theatre and continue to shape it today