philtrum

noun

1. The shallow vertical groove running from the nasal septum to the center of the upper lip.

   “Oral intercommissural distance (mouth width) and philtrum length are useful measurements for diagnosis of wide or large mouth (macrostomia), small mouth (microstomia), long philtrum and short philtrum and form ‘good handles’ in syndromic delineation.”

   “Upper lip reconstruction is more difficult than lower lip reconstruction because the upper lip has a central structure, the philtrum.[…]Wounds adjacent to the philtrum that are closed primarily may shift the philtrum to the affected side. However, with time, the philtrum will tend to return to its midline position.”

   “If the philtrum is long and deep, then these people are very romantic, sexual, lively and friendly.”

2. The junction between the two halves of an animal's upper lip or nose.