The line under the tongue, in most cases, refers to the lingual ligament, which is a ligament-like structure in the middle of the tongue’s abdomen, usually connecting the tongue’s abdomen to the floor of the mouth. In many children, the lingual ligament is short and the child’s pronunciation is slurred, so lingual ligament lengthening is performed to lengthen the ligament and correct the child’s pronunciation. The age limit for lingual ligament surgery is controversial. Most people believe that it is safer to perform lingual ligament surgery after the age of 1 year, and it is also the time when children start to exercise their voice after the age of 1 year, but some people suggest that lingual ligament surgery should be performed after the age of 3 or 4 years.