Dry mouth, also known as xerostomia, is a common condition where the saliva flow in the mouth is reduced, causing a persistent dry feeling. It can be caused by medications, diseases like Sjogren's syndrome or diabetes, cancer treatments like radiation, or aging. Symptoms include dry and cracked lips and mouth, difficulty speaking or swallowing, and a change in taste. Prevention focuses on stimulating saliva flow through staying hydrated, chewing sugarless gum, avoiding smoking and salty foods, and using over-the-counter saliva substitutes or treatments prescribed by a dentist.