Interrogative sentences are typically used to ask questions. There are three types of interrogatives: polar, alternative, and content. Non-manual markers play an important role in interrogatives in not only distinguishing them from other sentence types but also differentiating between different interrogative sub-types. However, which specific non-manual markers fulfill these functions is subject to dialectal variation. Moreover, some non-manual markers are more prominent, and thus easier to detect such as raised eyebrows whereas others are more subtle such as a slight backward head tilt (chin up) or a single slight head nod.
The position of the head distinguishes interrogatives from declaratives. In some dialects the head is forward in both polar and content questions whereas in some others while the head is forward in polar questions, it is backward in content questions. There are also other non-manual markers such as brow raise, head nod and head shake, which are described below. The spreading domains of these non-manual markers vary.