Tears are the liqui product of a process of lacrimation to clean and lubricate the eyes. The word lacrimation may also be used in a medical or literary sense to refer to crying. Strong emotions, such as sorrow or elation, may lead to crying. The process of yawning may also result in tearing. Although most land mammals have a lacrimation system to keep their eyes moist, humans are the only animal generally accepted to cry emotional tears.