Free indirect speech
A technique fusing the character's voice into the narrator's, with no reporting verb or quotation marks.
Free indirect speech reports words or thoughts without a reporting verb or subordination: "She closed the door. So that was their big news. To hell with them." Third person and narrative tense remain, but vocabulary, rhythm and judgments belong to the character — two voices sound in one sentence.
Perfected by Flaubert and Jane Austen, then generalized across the modern novel, it's the finest tool for sliding from narrative objectivity into a consciousness's subjectivity with no visible seam. It also enables irony: the narrator can let a character hang themselves with their own words, without comment.
Example
"He shrugged. What did he have to lose, after all? Nothing. Strictly nothing."