What is justified?

Photo source: Wikimedia Commons, Owen Williams

Photo license: CC BY-SA 3.0

What is justified? Here is my definition:

Justified is the attribute of being supported by a good reason

I believe there is a subjective line between justified and not-justified. I don't have a strict criteria for what constitutes as a good reason. For example, if I hear loud music playing next door, am I justified to believe they are having a party? Depending on who you ask, the answer could be yes or no. What constitutes as a 'good reason' is subjective.

License: CC BY-SA 4.0