Prosthion is a term that refers to the lowermost point of the nasal septum, located on the middle line of the upper lip. It is a point of interest for anatomists and dentists due to its relationship to facial measurements and dental occlusion. Some synonyms or related terms for prosthion include the subnasale, which is the midpoint between the nostrils, and the stomion, which is the midpoint of the mouth. Other related terms for prosthion include the translabial and transoral lines, which refer to imaginary lines drawn across the upper lip or mouth, respectively. These terms can be useful for clinicians and researchers studying changes in facial anatomy and dental occlusion.