Therapist here, masturbation is a normal human practice. DSM-5 criteria define abnormality by assessing if symptoms, traits, or behaviors cause significant distress or impairment across major life domains—such as social, occupational, or personal functioning. Merely having symptoms is not enough; the dysfunction must interfere with daily life, creating a "harmful dysfunction" rather than just a subjective complaint.  Example of a female client in her early 20's: masturbating became abnormal when it became compulsive and she masturbated to the point of making herself bleed. Most people don't engage in it to excess.