What does "considered opinion" mean? How is it different from "opinion"?

Native speaker’s answer
Rebecca
A "considered opinion/thought" refers to one's opinion after they have given a lot of consideration or thought towards something. It's not an expression that's used very frequently, however. Most people prefer to use "in my opinion/my opinion is that ..." when speaking. Ex: My considered opinion is that we must work together towards a greener future. Ex: In my opinion, we should work together towards a greener future.