protagonist's dialogue could be switched with whole sections of another main character's dialogue, you haven't done an effective job of using speech to individualize them. Go back and rewrite. Give each a diction, a rhythm, a slant on the world (the essence of characterization) of his or her own.
An aside here: Dialogue is the one place in fiction where cliches can work well. If your character's thoughts and ideas are hackneyed and undigested, cliched speech will convey that. In that sense, dialogue is a horse of a different color. If your character never has an original thought in her pretty head, let her spout cliches till hell freezes over. Just be aware that she may sound dumb as a fence post.
I DON'T LIKE YOUR TONE:
MAKING DIALOGUE CARRY EVEN MORE WEIGHT
By one expert estimate, 70 percent of communication is nonverbal. If Harry says to Sue, ''Can I see you tonight?'' almost three-quarters of his meaning will be conveyed by the tone of his voice, his inflections, his facial expression, his hand gestures, his body language, the degree of his attention.
Perhaps he says, ''Can I see you tonight?'' in a weary tone of voice, while watching another woman cross the street, with the corners of his mouth turned down. or perhaps he says it intently, his eyes on Sue's face, his whole body yearning forward. Each sentence will convey entirely different meanings to Sue, despite identical words.
In fiction, dialogue doesn't have the powerful support of these nonverbal clues. You can, of course, describe some of them: Harry's gestures, Sue's tone of voice. And you should. But you may also need to increase the emotional level of the words themselves, to compensate for the loss of nonverbal communication.
For instance, suppose a character named Stan has just learned of another character's death. If you were a playwright, you could write Stan's line as ''Tom was a good man.'' The actor would supply the emotion with which the line should be said: resignation, irony, anger. But we fiction writers don't have John Malkovich or Meryl Streep to lend color to our prose. We have to do it ourselves. Therefore, you might heighten Stan's dialogue to ''Tom was a good man. Damn it, he was such a good man!'' The extra words, the mild profanity, the exclamation point—all make clear that Stan's emotion is anger that this good man is dead.
You might also use both heightened dialogue and description of nonverbal cues:
''Tom was a good man,'' Stan said softly. He fumbled with a cigarette, lit it, dropped it on the carpet. And then, ''Damn it, he was such a good man!'' He looked out the window, dry-eyed, and the rug smoldered at his feet.
Here, dialogue that might seem theatrical in real life combines with distraught action to add layers of emotion to the little speech.
YOU WEREN'T LIKE THAT YESTERDAY: CONSISTENCY IN DIALOGUE
This is a tricky subject. Yes, you want your character to speak consistently from one page to the next. A teenage girl who says, ''So I go, 'He didn't tell me that!' I was, like, totally grossed out,'' is not the same teenage girl who says, ''I respond to the alienation in the novels of Camus.'' If you try to make her the same girl, we probably won't believe it.
on the other hand, everyone has more than one mode of speech. You undoubtedly use different language and sentence structures to your best friend, your six-year-old niece and the cop who has just stopped you for speeding. Good dialogue should capture this difference—while still sounding like the same person.
An example. Two characters are having an amiable discussion about where to have lunch. They decide, walk down the street to the restaurant, and one ducks briefly inside the post office to buy stamps. The other, waiting outside, is suddenly lunged at by a mugger who kicks him in the kneecap and grabs his wallet. The character falls to the ground, scraping his left hand and right palm. He no longer sounds amiable. In fact, he yells something unprintable in this
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