Using the "pause" and "silence" in scriptwriting...

Probably the most important nonverbal element in scriptwriting, especially playwriting, is the pause, or silence in the middle of a line or between lines of dialogue.  Often the most potent moment in a scene is during the silence that ensues after a poignant line, that moment when a profound decision or realization is made.  The audience witnesses this happening during the silence.

These moments are very much part of the writing.  You are creating a script that includes both verbal and nonverbal elements, and it's how the two interplay with each other that determines the shape and rhythm of each scene.  All nonverbal physical actions influence how your characters relate to each other and what they say and think.  And this is especially true for silences.