An intentional or negligent failure to act reasonably, according to law, or according to duty; it is a wrong act or error that causes injury to another person. The wrong act or error can arise out of ignorance, carelessness, negligence, or even unskillfulness. This means that not knowing any better, not taking proper precautions, not taking into account those around you, or even lacking the skills necessary to perform a function can all be considered acts of fault if the result is injury to another. The most common use of fault is in relation to car accidents, where the term appears often (i.e. Who was at fault? A no-fault insurance claim. My client was found to have no fault in this accident, et cetera).