Final answer:
False, Scientific theories are not guesses. They are well-substantiated explanations based on evidence and rigorous testing. They are different from everyday use of the word theory.
Step-by-step explanation:
A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experimentation. Theories are not guesses or hunches; they are explanations that have withstood rigorous testing and verification. They are supported by a large amount of evidence and can satisfactorily explain numerous observations. Theories are not likely to change easily, and if they do, it is because there is overwhelming evidence that contradicts the theory. So, scientific theories are very different from everyday use of the word theory, which may refer to guesses or speculations.