Adding Meaning with Internal Dialogue
As your viewpoint character talks and listens to others talking, you have the opportunity to weave in dialogue that shows the character's thoughts. Inner dialogue, used in this way, can add a new dimension to dialogue.
Here is an example from Chimamanda Ngozi Adichie's Purple Hibiscus.
I meant to say I am sorry Papa broke your figurines, but the words that came out were, “I am sorry your figurines broke, Mama.”
With the combination of internal and spoken dialogue, the author is able to show both what the character wants to say and what she actually says.
Here is another example, this one from Margot Livesey's Eva Moves the Furniture. Notice how the dialogue can work with the internal dialogue to tell a more complete story.
In the waiting room, Matthew dropped the newspaper and stood to meet me. “Eva.” He put his hands on my shoulders. “Are you all right?”
Through my dress I felt his touch, warm and sure and for a moment I wanted to throw myself into his arms. I had to swallow before I could repeat Sir Hamilton's verdict.
“Splendid,” he said. And suddenly, seeing his face break into a smile, I understood that my uncertain health had not entirely passed him by. He bent to kiss me.

