What is the difference between an opinion and a theory

An opinion is what someone might think with no evidence. A theory always has some kind of evidence.

An opinion is what someone thinks with completely no evidence, whatsoever and a theory is what something thinks but with some kind of evidence. For example, this is my opinion but with other peoples opinion it has become a theory because I have evidence. Also theories are used in crime solving, as they have evidence to go on. Hope this helps.