Sexual abuse, also referred to as molestation, is the forcing of undesired sexual behavior by one person upon another, when that force falls short of being a sexual assault. The offender is referred to as a sexual abuser or molester. The term also covers any behavior by any adult towards a child to stimulate either the adult or child sexually. When the victim is younger than the age of consent, it is referred to as child sexual abuse.

A central characteristic of any abuse is the dominant position of an adult that allows him or her to force or coerce a child into sexual activity. Child sexual abuse may include fondling a child's genitals, masturbation, oral-genital contact, digital penetration, and vaginal and anal intercourse. Child sexual abuse is not solely restricted to physical contact; such abuse could include noncontact abuse, such as exposure, voyeurism, and child pornography. Abuse by peers also occurs.

Sexual assault is an assault of a sexual nature on another person. Although sexual assaults most frequently are by a man on a woman, it may be by a man on a man, woman on a man or woman on a woman, or adult on a child. Approximately one in six American women will be a victim of a sexual assault in their lifetime. Largely because of child rape and prison rape, approximately ten percent of rape victims are males.

While sexual assaults are associated with the crime of rape, it may cover assaults which would not be considered rape. What constitutes a sexual assault is determined by the laws of the jurisdiction where the assault takes place, which vary considerably, and are influenced by local social and cultural attitudes.

Incest is sexual activity between closely related persons (often within the immediate family) that is illegal and socially taboo. Most incest cases reported in scientific studies are between adults and prepubescent or adolescent children, and particularly between fathers or other male relatives, and girls. This is a form of child sexual abuse that has been shown to be one of the most extreme forms of childhood trauma, a trauma that often does serious and long-term psychological damage, especially in the case of parental incest. 

Adults who were incestuously victimized by adults in their childhood often suffer from low self-esteem, difficulties in interpersonal relationships, and sexual dysfunction, and are at an extremely high risk of many mental disorders, including depression, anxiety, phobic avoidance reactions, somatoform disorder, substance abuse, borderline personality disorder, and complex post-traumatic stress disorder.

Domestic violence, also known as domestic abuse, spousal abuse, child abuse or intimate partner violence (IPV), can be broadly defined as a pattern of abusive behaviors by one or both partners in an intimate relationship such as marriage, dating, family, friends or cohabitation. Domestic violence has many forms including physical aggression (hitting, kicking, biting, shoving, restraining, throwing objects), or threats thereof; sexual abuse; emotional abuse; controlling or domineering; intimidation; stalking; passive/covert abuse (e.g., neglect); and economic deprivation. Domestic violence may or may not constitute a crime, depending on local statues, severity and duration of specific acts, and other variables. Alcohol consumption and mental illness have frequently been associated with abuse.

Awareness, perception and documentation of domestic violence differs from country to country, and from era to era. Estimates are that only about a third of cases of domestic violence are actually reported in the United States.