Final answer:
A well-established hypothesis is called a theory, a well-substantiated explanation for observed phenomena that has undergone rigorous testing and confirmation.
Step-by-step explanation:
A well-established hypothesis is often called a theory. A hypothesis is a tentative explanation for an observation, which can be tested and refined through experimentation and further observation. When a hypothesis has been repeatedly tested and confirmed, it can become a scientific theory, which is a well-substantiated explanation of some aspect of the natural world. Scientific theories are accepted because they offer satisfactory explanations and have predictive power, but they are open to modification if new data warrant it. In contrast, a scientific law describes the behavior of an aspect of nature, often in a succinct mathematical form, but without explaining why that behavior occurs.