A belief is a firm thought that something is true, often based on revelation. Belief is usually a part of belonging to a religion. It is different to scientific knowledge that can be tested, but belief is not able to be tested. For example, a person may believe in God or gods. The word is also used to describe what a person expects will happen based on limited information. For example, "I believe Amy will come around today". Belief is also something you believe in but you cannot prove exactly.
Belief Facts for Kids. Kiddle Encyclopedia.