Modern playwrights' styles are varied, but some trends can be found in their diverse work. Generally, modern drama is thought to have started with Ibsen's A Doll's House. One trend found in modern drama that certainly shows itself in A Doll's House is the idea that the playwright leaves the meaning/motivation for actions open to interpretation. The audience can speculate about Nora's true reasons for her decision, and things are not left in a neat, tidy package at the conclusion of the play. Absurdest playwrights such as Beckett, Shepard and Pinter who fall in the modern era take this "open to interpretation" approach to another level, using circular structure and taking the focus away from surface-level plot interpretation.
Another trend can be seen in the breaking of stereotypes for, most notably, female characters. Ibsen, Shaw, Churchill, Wilde, and Williams are all noted for standout females.
The inclusion of humor also became more prevalent in the modern era, especially looking at Oscar Wilde's intricate witty dialogue.
Theaterpro.com describes the origins of modern drama in this way:
Modern drama as we know it in the twentieth and twenty-first century began when Nora slammed the door on her family in Ibsen’s A Doll’s House. Together with Strindberg and Shaw, Ibsen swept away romantic melodrama heavy with the passions of stereotypical heroes and heroines to create dramatic works that presented real-life characters in action that reflected and questioned prevailing morals and mores. Dialogue, once florid and poetic became sharp, pointed, and often witty.