A belief that is known to be accurate is knowledge, and a belief that MAY not be accurate is an opinion. Knowledge is based on a fact or a good source, belief is mainly based on emotions, and opinions can be seen as a combination of the two as there are some facts involved and also saturated with emotions.

https://prezi.com/p/ajghj9mqm8kl/how-can-we-distinguish-between-knowledge-belief-opinion/

Although these definitions seem totally different, it is often difficult to distinguish between “what we truly know” from “what we believe to be true”. This is because we never have the time, skills, materials and will to carefully check every single thing in life, so we have to rely on information supplied by others. Also, human process of learning is really very effective for survival in the warm climate wilderness, but when we apply it to science, moral judgement and other important things, we find that it is prone to all sorts of cognitive biases and logical errors.

So, to know what we know, we need to really carefully examine the evidence and the biases involved in its gathering and interpretation. Asking himself “what do I really know” Descartes arrived to the conclusion that “I think, therefore I am” is just about the only thing that can reliably be known and proceeded to develop his theory based on that.

Beliefs, on the other hand, are subjective (in that they are primarily held by an individual and are not verified by any objective method of verification), nevertheless they are high on the sense of certitude. It is important to remember that certitude does not mean infallibility; rather it merely indicates how sure one feels about one’s beliefs. Of course, someone could also hold a ‘belief’ loosely. But we shall retain the term opinion for such, irrespective of what is held—be it something as insignificant as a preference for certain food or something as significant as an article of religious faith. A belief, therefore, would be characterised by something stronger, and in some cases, it could be so strong that we may call it conviction. Despite how significant it may be for someone, a belief has nothing in itself that makes it necessarily true—neither the sense of certitude accompanying a belief nor the total sincerity with which a belief is held can assure the truth of the belief.

Unlike opinion or belief, Knowledge, especially propositional knowledge (we aren’t talking about knowledge in the sense of an ability or a skill but a statement or an affirmation that is either true or false) is a belief that can be verified and understandably carries with it a high sense of certitude. In fact, a classical account of knowledge defines it as “justified true belief.” By that definition, knowledge has to fulfil the criteria: a) of being a belief, b) of being true, and c) of being justified.

Opinions are generally held loosely with a low sense of certitude. They are also subjectively held and need not be shared by others. They could be about preferences for a certain type of music, or tastes pertaining to food, or views about politics or a particular sport. It would really be silly to argue against my friend’s opinion that the best dosas are made in Bangalore. And even if I were to argue that the best ones are made in Chennai, our positions merely indicate what our preferences are rather than the “truth” about it.