Final answer:
The phrase 'theory of evolution' refers to an explanation that has been thoroughly tested and supported by substantial evidence, contrasting with a hypothesis, which is a tentative suggestion pending further research.
Step-by-step explanation:
The word theory in the phrase 'theory of evolution' is best replaced by explanation. In scientific terminology, a theory is a well-substantiated explanation of an aspect of the natural world that is supported by a significant body of evidence and often incorporates laws, hypotheses, and facts. The term theory is used to describe concepts that have been repeatedly tested and are widely accepted within the scientific community.
An hypothesis, on the other hand, is a tentative explanation for an observation and serves as a starting point for further investigation. In the context of the question, hypothesis is closest in meaning to a suggestion. This distinction underscores the robustness of a scientific theory compared to the preliminary nature of a hypothesis.
A scientific law describes the behavior of an aspect of nature, often in the form of a mathematical formula. It does not explain the phenomena but rather describes a consistent relationship observed in nature. Therefore, whereas a law describes what will happen under certain circumstances, a theory explains why it happens.