515 is a numerical expression that is commonly utilized, particularly in the United States, to refer to someone who is mentally unstable or insane. The term is derived from 5150, which is a California Welfare and Institutions Code that authorizes the involuntary psychiatric hold of an individual who poses a danger to themselves or others due to their mental condition. The number 5150 has gained widespread recognition in popular culture, such as music and movies, which has led to the abbreviated form "515" being used colloquially.

Referring to a person as "515" implies that they exhibit behaviors or characteristics associated with mental illness, encompassing a broad range of mental disorders and conditions that affect an individual's thoughts, emotions, and behavior. It is important to highlight that using the term "515" can be derogatory and stigmatizing, perpetuating the negative stereotypes around mental health issues.

The use of this term in a derogatory manner is considered offensive, as it reinforces the societal marginalization and discrimination faced by individuals with mental illnesses. Instead, it is crucial to promote empathy, understanding, and support for individuals who might be experiencing mental health challenges. Properly addressing mental health issues involves starting conversations, raising awareness, and seeking appropriate help and treatment for those in need.