What is a scientific theory is and under what conditions a theory may be revised?

A theory does not explain but it states the relationships between variables. It can be revised at any time if someone disagrees with it.
A theory is an explanation for a scientific phenomenon. It answers WHY and HOW type questions about the natural world. A theory is based on extensive testing and experimentation and is taken as truth. Sometimes, however, a theory must be revised. This happens when new knowledge or new technology expands and corrects our understanding.
A theory is only a guess and can be revised by anyone.
A theory is an explanation for a scientific phenomenon. It answers WHY and HOW type questions about the natural world. A theory is based on extensive testing and experimentation and is taken as truth. It can NEVER be revised.