A scientific hypothesis is a possible explanation for a set of observations or answer to a scientific question. A hypothesis is not a fact, but one possible way to explain a group of observations. It is important for a scientific hypothesis to be testable. A scientific theory is a well-tested explanation for a wide range of related observations or experimental results. Like a hypothesis, which is not accepted until it is tested repeatedly, a theory is accepted by scientists only when there is a large body of evidence that supports it. As with a hypothesis, scientists will modify or discard an accepted theory if future testing proves it to be incorrect. However, unlike a scientific hypothesis or scientific law, a scientific theory explains many different but related observations. A scientific law describes a pattern observed in nature. Unlike a scientific hypothesis or a scientific theory, a scientific law does not attempt to explain the pattern. Like a hypothesis or a theory, a law is based on evidence from observation or experimentation. Scientific laws can be thought of as rules of nature.