Having Trouble With The Language?
The law is complex, to become a lawyer requires years of study, often working under an experienced lawyer and an exam. Self-defense law is no different.
One way to see this complexity is to look at your State's, Province's, or other government divisions statutes on use of force. In my State, Pennsylvania, the laws would leave a lot of room. According the statute, force is justifiable "when the actor believes that such force is necessary for the purpose of preventing himself against the use of unlawful force". There are limitations, it is unlawful to resist arrest, or resist force is the other party is using force to protect their property . The law is clear in saying that if "The actor knows he can avoid the necessity of such force with complete safety by retreating".
Like many states in the United States, Pennsylvania has a "Stand Your Ground Provision', this provision gives a person to right to use deadly force without giving the other party an opportunity to retreat. This provision comes with conditions; the party using the force must have a right to be in the place, the law is likely intended to be applied in a home or vehicle, the party using the force must believe it is necessary, and this would need to be proven, and the person the force is used against must display either a firearm or replica or any other weapon readily or apparently capable of lethal use.
This complexity leads What you Don't Know can Kill you to say self-defense is less about what you do, and more about what you don't do! Questions about; if you need to engage, do you have enough force to engage or have you used too much, and when to end the encounter are decisions, often made in split-seconds.
What happens before the encounter is important. One must avoid participating in the creation and escalation; one ego, and adrenaline must be controlled, and encounters need to be avoided if possible. There is a concept of "Actions and Responsibility"; you and the rest of a bloc decide to block a group a fasc, chanting "Whose streets, our streets", an attorney may argue that was provocation.
There are other words that matter in self-defense; justified, immediate threat, aggravated assault and duty to retreat. These concepts are also ones that an attorney would understand better than the average citizen.