An overbite means that the upper and lower jaws are not aligned properly. The lower jaw may be too small or the upper jaw may be too big, causing the upper teeth to be too far forward or the lower teeth to be too far back, resulting in too much distance between the upper and lower incisors. The causes could be genetic or developmental in nature.

However, in almost all people, the upper row of teeth minimally overlaps the lower row. Only when the position of the teeth deviates too much from this norm, it is referred to as overbite in medicine. A distinction is made between horizontal misalignment (overjet) and vertical misalignment (overbite).