A cleft is any opening in a normally closed structure. A cleft lip is an opening in the lip, typically the upper lip. These clefts are more commonly unilateral (on one side of the lip) as compared to bilateral (on both sides of the lip). Unilateral clefts occur more frequently on the left side of the mouth. A cleft palate is an opening on the roof of the mouth. Clefts can be found in the hard palate (towards the front of the mouth), soft palate (more towards the back of the mouth) or both.