The Function Of Dialogue

The Function Of Dialogue

Dialogue needs to accomplish at least one, preferably more, of the following:
• further the plot
• reveal character
• create conflict
• elicit emotion
• deepen our experience of what we see on screen

In the movie Some Like it Hot, written by Billy Wilder and I.A.L. Diamond, Jerry (Jack Lemmon) and Joe (Tony Curtis) are down-and-out musicians who have witnessed a mob hit. Broke and desperate to get out of town alive, they masquerade as women and join a girl's band. Still awkward in their skirts and high heels, they're standing on the platform waiting for a train. Just then, band member Sugar (the ultra-feminine Marilyn Monroe) strolls by carrying her ukulele. Here's what Jerry says:
JERRY
Who are we kidding? Look at that--look how she moves—-it's like Jell-O on springs. They must have some sort of a built-in motor. I tell you it's a whole different sex.

This dialogue furthers the plot by foreshadowing the trouble our heroes will have pulling off the masquerade. And, by adding nuance to the images we see on screen, it introduces us to Sugar, a major character.
It also exemplifies the conflict of men trying to pass as women, especially in the presence of someone like Sugar, and hints at the additional conflict that's sure to come when two men vie for the attention of one beautiful woman.
The line reveals character, too. We see Jerry's nervousness and his wittiness. We see he's fascinated and intimidated by Sugar.
By poking fun at sexuality and identity, this dialogue makes us laugh and sympathize with Jerry. So it elicits emotion, too.
If a line of dialogue doesn't further the plot, reveal character, create conflict, elicit emotion, or deepen our experience of what we see on screen, get rid of it. As painful as it can be, all serious writers must develop the discipline to cut any dialogue that doesn't serve the story.