| Eyes wearing |
Philosophy of science
“”It is difficult to make predictions, especially about the future.
|—Karl Kristian Steincke|
Prediction in an informal sense means something like "guess" or "idea". If you want to stretch a bit, it can also mean "prophecy" (in the temporal sense).
In a scientific sense prediction refers to the ability of a hypothesis to accurately forecast what will happen under specific conditions. In order to test a hypothesis a scientist will make a prediction based on the hypothesis. If the result of the experiment is in accordance with the prediction then the hypothesis has not been disproven. (It has not been proven either, rather supported.) The scientific method is built upon repeated iterations of this process.
Hypotheses which are not able to make such testable predictions are frequently pseudoscience. Pseudoscience is almost universally characterized by the inability to make meaningful, specific predictions constructed from the core pseudoscientific theory.