In legal terms, "negligence" is the word used to describe any careless behavior that causes or contributes to an accident. For example, if a driver is talking on their cell phone and hits your car while you're stopped at a red light, that driver is probably negligent. It is the failure to use the care that a reasonable person in the same or similar circumstances would use.
Elements to prove negligence:
Generally, in order to prove that someone was negligent and win your lawsuit, you must be able to prove the following five things.
Duty (or the obligation to be careful)
A legal obligation imposed on an individual requiring that they adhere to a standard of reasonable care while performing any acts that could foreseeably harm others. The question most commonly asked is "Did the defendant (negligent party) owe a duty to the plaintiff (injured party)?" Duty arises in many forms. For example, drivers have a duty to all the other drivers on the road to drive in a safe manner.
Breach of Duty (or failure to be careful)
After defining the duty, evidence must be introduced to show whether or not the defendant breached the duty with respect to the plaintiff. In order to prove this element, you must show that the defendant failed to act like a reasonable person would in fulfilling the duty owed to the plaintiff.
Causation of Harm
This is commonly called the "but-for" test. If you can show that, but for the defendant's actions, the plaintiff would not have been injured, then you have satisfied this element. For example, but for the water left in the entrance of a grocery store, the patron would not have been injured. This relates to the proximity of the defendant's actions to the harms at issue in the lawsuit. For example, if the defendant hit and injured a fellow driver who sustained a neck injury while driving, and then at the hospital, the injured person called her husband to tell him about his broken neck, and the husband suffered a heart attack, this may be outside the proximate cause of the defendant's actions. The purpose of this element is to promote practicality and fairness, and often asks whether it is fair to attribute the injury to the defendant's actions.
Were Defendants Acts/Omission a Substantial Factor in Causing Harm?
Not only do the defendant's acts/omissions need to be "a cause" of harm, but must also be a substantial factor in causing the harm that a reasonable person would consider to have contributed to the harm. It must be more than a remote or trivial factor. It does not have to be the only cause of the harm.
Damages (or harms, losses, etc.)
Finally, you must be able to prove that you were actually harmed, damaged or suffered losses in order to prevail in your lawsuit. In a personal injury case, damages often include medical bills, lost earning capacity, and lost wages as well as damages for pain and suffering and even punitive damages (additional damages assessed for intentionally wrongful conduct which is designed to deter wrongful conduct in the future).
Not every accident is caused by negligence and not every negligent act results in holding a person at fault for their actions. It is best to seek the consultation of an experienced personal injury attorney in your area to determine the potential negligence of all the people involved in an your accident/incident.