self-defense or private defense is a countermeasure that involves defending oneself, one's property, or the well-being of another from harm. The use of the right of self-defense as a legal justification for the use of force in times of danger is available in many jurisdictions, but the interpretation varies wide.
Physical self-defense is the use of physical force to counter an immediate threat of violence. Such force can be either armed or unarmed. In either case, the chances of success depend on a large number of parameters, related to the severity of the threat on one hand, but also on the mental and physical preparedness of the defender.
Many styles of martial arts are practiced for self-defense or include self-defense techniques. Some styles train primarily for self-defense, while other martial or combat sports can be effectively applied for self-defense. Some martial arts train how to escape from a gun situation, or how to break away from a punch, while others train how to attack. To provide more practical self-defense, many modern day martial arts schools now use a combination of martial arts styles and techniques, and will often customize self-defense training to suit the participants' lifestyles, occupations, age groups and gender, and physical and mental capabilities.
Self-defense techniques and recommended behavior under the threat of violence is systematically taught in self-defense classes. Commercial self-defense education is part of the martial arts industry in the wider sense, and many martial arts instructors also give self-defense classes. While all martial arts training can be argued to have some self-defense applications, self-defense courses are marketed explicitly as being oriented towards effectiveness and optimized towards situations as they occur in the real world. It should not be presumed however that sport based systems are inadequate, as the training methods employed regularly produce well conditioned fighters experienced in full contact fighting. There are a large number of systems taught commercially, many tailored to the needs of specific target audiences (e.g. defense against attempted rape for women).