This refers to a condition where the upper jaw is narrow.
Some signs of this are upper crowded front teeth and/or the side and back teeth biting inside of the lower teeth, on one or both the right and left sides.
With a narrow jaw, the smile appears narrow rather than broad and spaces can be seen on the side of the smile, rather than where the teeth should be.
The upper jaws are connected with the nose and in children with narrow upper jaws, the nose passage is smaller. A common reported problem from parents, is their child tends to breathe through the mouth, or snore at night, or wake up in the morning with a dry mouth due to mouth breathing.
Narrow jaws can be one of the causes of heavy mouth breathing- which in a child, can change
There is a window of time where the upper jaw bones and their connections have not hardened in a child and early teen, where the upper jaw can widened effectively without surgery.