Crowding is an orthodontic problem when one has too much tooth structure in too little of a space.
Spacing is the opposite of crowding where tooth structure has to be consolidated (upper photos) or added (lower photos). Arrow points to a diastema which is simply a space between two teeth.
An openbite results when all the teeth do not close together at the same time. Thumb-sucking can cause an openbite. This can be corrected with standard orthodontic means most of the time. (The top photo is of an improper jaw requiring surgery in an adult. The patient in the bottom photo only required a thumb guard).
An underbite results when the upper teeth fit inside the arch of the lower teeth. This is usually a growth discrepancy and may require surgery if excessive.
Normally, the upper teeth are in front of the lower teeth Blue arrows point to an anterior crossbite. Red arrow points to a posterior crossbite.
An overjet is the projection of the top jaw forward of the bottom jaw. There may be crowding, additionally. Depending on the severity, growth modification appliances, extractions, or surgery in adults may be required.
The teeth are angled outward, “protruding” from the mouth. (More commonly called “buck teeth”)
Opposite of a protrusion… teeth are angled inward.