Definition:

A yes-no question that has the form of a declarative sentence but is spoken with rising intonation at the end.

Declarative sentences are commonly used in informal speech to express surprise or ask for verification. The most likely response to a declarative question is agreement or confirmation.

See also:

• Cooperative Principle
• Echo Question
• Embedded Question
• Exclamatory Question
• Queclarative
• Question

• Tag Question
• Twelve Types of Questions in Casablanca

Examples and Observations:

• "You think I'm kidding you? You think it's a joke to have to walk home on a clear night with an umbrella? You think that because I'm quirky I don't hurt? You've got it backwards. I'm quirky because I hurt."
  (Jack Weston as Danny in The Four Seasons, 1981)
• Henry Rowengartner: Wow, you ate that whole thing?
  Frick: Why, sure! It wasn't that much.
  (Rookie of the Year, 1993)
• Vivian: I was supposed to ride that barrel right out of this crummy town.
  Jaye: And you never considered a bus?
  ("Barrel Bear," Wonderfalls, 2004)
• "A declarative question has the form of a statement:

  You're leaving?

  but has the intonation of a question when spoken and is marked by a question mark in writing.
  
  "A declarative question differs from a rhetorical question such as:

  Do you think I was born yesterday?

  in two ways:
  1. A rhetorical question has the form of a question:

     Was I tired?

  2. A declarative question seeks an answer. A rhetorical question requires no answer since it is semantically equivalent to an emphatic declaration:

     Do you think I'm stupid? (i.e. I'm certainly not stupid)
     Am I tired? (i.e. I'm extremely tired.)

  (Loreto Todd and Ian Hancock, International English Usage. Routledge, 1986)