Table 2.

The study parameters and their definitions.

Parameter	Definition
Hard-palate length	Distance between the anterior nasal spine (ANS) and the posterior nasal spine (PNS)
Velopharyngeal depth	Distance between the PNS and the posterior pharyngeal wall on the plane parallel to the hard palate
Velar length	Distance between the PNS and the tip of velum on the curvature along the velum
Velar thickness	Distance between the velar knee and velar dimple
Retroglossal space	Distance between the tongue and posterior pharyngeal wall on the plane parallel to the hard palate and through the anteroinferior border of the second vertebra (C2)