A shout, scream, yell, shriek, hoot, holler, vociferation, outcry, or bellow is a loud vocalisation in which air is passed through the vocal folds with greater force than is used in regular or close-distance vocalisation. This process can be performed by any creature possessing lungs, including humans. There are slight differences in meaning amongst them; for example, "scream" and "shriek" generally refer to a higher-pitched, sharp sound, used by some birds and other animals, and a "hoot", such as emitted by an owl, usually does not involve words.A scream is often an instinctive action, with a strong psychological aspect, like fear, pain, surprise, happiness, anger and others.