Rheum discharge, commonly known as eye discharge, refers to the moisture that accumulates in the corners or edges of the eyes during sleep or upon waking. In medical terms, it is called "rheum." However, there exist several synonyms for this condition, including "eye gunk," "sleep sand," or "eye crust." The thick, often yellowish or greenish discharge can also be referred to as "eye mucus" or "eye goop." These terms describe the same phenomenon of the body's natural defense mechanism, which helps to remove dirt, debris, or excess tears, keeping our eyes clean and lubricated. While the terminology might differ, the presence of rheum discharge is a harmless occurrence that can easily be wiped away for fresh, clear vision.