Some of the terms used to describe orthodontic concepts are defined below. The terminology sometimes is different in different countries.
| Term | Also called | definition |
| Malocclusion | An arrangement of the teeth that is not ideal. | |
| Skeletal Malocclusion | jaw size discrepancy | A anomaly of the jaw growth that is disproprotionate sufficient to cause noticable facial disharmony or asymmetry. A dental malocclusion is often secondary to a skeletal disproportion |
| Occlusion | the way the teeth bite together | |
| Class 1 occlusion | normal occlusion, ideal occlusion | The ideal biting relationship (most common Caucasian bite) commonly about 2-3mm horizontal overlap |
| Class 2 occlusion | increased overjet, | The lower teeth are behind the Class 1 position, the overjet is usually more than 3mm |
| Class 3 Occlusion | reverse overjet, underbite, bulldog bite | The lower teeth are biting in front of the ideal position. The overjet is less than 1mm and often reversed |
| Eruption | The growth of the teeth into the mouth and into an occlusion with the teeth in the opposing jaw | |
| Overjet | often confused with overbite by laypersons | horizontal overlap of the upper incisors compared to the lower incisors ideal is usually approx 2-3mm |
| Overbite | Vertical overlap of the upper incisors compared to the lower incisors -ideal usually approx 2-3mm | |
| Incisor teeth | 4 Front teeth either side of the midline | |
| Canine Teeth | Third tooth from the midline (often fang shaped) | |
| Premolar teeth | (teeth before the molars) positioned 4th and 5th from the midline | |
| Molar teeth | large double teeth at the back of the mouth. comprising 1st molars, 2nd molars (12 year old molars) and 3rd molars (wisdom teeth ) | |
| Alignment | how well the teeth fall on an ideal arch shape | |
| Angulation | AKA tip – a tilt of a tooth along a horizontal axis perpendicular to the arch | |
| Inclination | AKA Torque a tilt of a tooth along a horizontal axis parallel to the arch | |
| Rotation | a twist of a tooth along its long axis | |
| Levelling | reducing the overbite to normal | |
| Relationship | similar to ‘occlusion’ how close to ideal the teeth bite | |
| Crowding | The amount of excess dental tissue to the arch length | |
| Arch length | The length of the average line judged to describe the shape of the dental arch | |
| Fixed appliance | A brace that is bonded to the teeth | |
| removable appliance | A brace that is removable | |
| TAD | mini screw, micro screw, mimi-implant | A small screw temporarily inserted into the jawbone like a piercing |
| RPE | Rapid Palatal expansion | |
| MARPE | BARPE | Miniscrew assisted rapid palatal expansion (bone anchored rapid palatal expansion) |
| SARPE | Surgically assisted Rapid palatal expansion |
