Xerostomia: Dry mouth. The condition of not having enough saliva to keep the mouth wet due to inadequate function of the salivary glands. Everyone has a dry mouth once in a while when they are nervous, upset or under stress. But if someone has a dry mouth all or most of the time, it can be uncomfortable and can lead to serious health problems. Dry mouth can cause difficulties in tasting, chewing, swallowing, and speaking. If it goes untreated, severe dry mouth can also lead to increased levels of tooth decay and infections of the mouth such as thrush.

Severe dry mouth is not a normal part of aging. It can be a clue to serious systemic diseases such as Sjogren syndrome, systemic lupus erythematosus, rheumatoid arthritis, scleroderma, sarcoidosis, amyloidosis, and hypothyroidism.

The word xerostomia reflects its Greek origins from "xeros" (dry) + "stoma" (mouth).