Final answer:
A scientific theory is a thoroughly tested and confirmed explanation of a natural phenomenon, whereas everyday use of 'theory' often refers to a guess or assumption. Scientific theories like evolution and cell theory have extensive empirical support.
Step-by-step explanation:
In everyday language, the term theory is often used to refer to a guess or an assumption about why something happens. For instance, saying 'I have a theory about who took the last cookie' implies a level of uncertainty and lacks rigorous proof. Conversely, in the scientific community, a theory refers to a well-substantiated explanation of some aspect of the natural world that is acquired through the scientific method and repeatedly tested and confirmed through observation and experimentation. Such theories are based on empirical evidence and are highly reliable within the limits of scientific understanding at the time.
To convince someone who doubts scientific explanations because they consider them 'just theories,' it's important to clarify that scientific theories are not mere guesses. Scientific theories, like the theory of evolution or cell theory, have extensive experimental and observational support. They are the cumulative and coherent body of knowledge, which stands until sufficient evidence might emerge to challenge them, leading to either refinement or replacement with a more accurate theory. This rigor and reliability separate scientific theories from the everyday use of the term.