has part has part characteristic of inheres in has modifier Narrow mouth The width of the mouth varies with facial movement and must be assessed when the subject has a relaxed (neutral) face. This term replaces microstomia, small oral aperture, and small mouth because the reduced opening of the mouth is secondary to reduced width. SNOMEDCT_US:14582003 Microstomia HP:0002261 Small mouth Small oral aperture UMLS:C0026034 HP:0009096 HP:0000160 HP:0009095 Distance between the commissures of the mouth more than 2 SD below the mean. Alternatively, an apparently decreased width of the oral aperture (subjective). Narrow mouth Abnormality of mouth size abnormal decreased width mouth