A common misconception is that rapes must happen by force. People often visualize a bloody, battered victim who yelled and tried to fight back against a stranger who pulled them into the bushes. This is a very  unlikely scenario for a variety of reasons, one being that 75-85% of sexual assaults are perpetrated by someone the victim knows, not a stranger. Often, the perpetrator is a friend or a loved one, possibly even a spouse or partner. Definitions of Sexual assault/abuse/rape all can include "lack of consent". When someone is drugged, unconscious, asleep, under the influence of drugs or alcohol, disabled and unable to understand the situation, or too young, or in a situation where they are compromised and unable to make a reasonable decision, they lack they ability to consent to sex. No resistance is necessary. Federal rape law is: "Penetration, no matter how slight, of the vagina or anus with any body part or object, or oral penetration by a sex organ of another person, without the consent of the victim."
State laws vary.

Unfortunately, many people who are sexually abused are "frozen" with fear or dissociated at the time of their assault and are unable to fight, yell, or struggle. This sadly leads them to inappropriately blame themselves or for others to blame them for the abuse instead of the one truly at fault, the perpetrator.