Opinion

We use opinion as a noun to mean beliefs or judgements about someone or something. When it refers to the beliefs or judgements of individuals, it is countable:

I’ve never agreed with Chris’s opinion on taxation.
A lot of people have strong opinions about bullfighting. (referring to their individual opinions)

When it refers to the beliefs or judgements of a group of people, opinion is usually uncountable:

The government is worried about public opinion.

We use phrases such as in my opinion, in your opinion, in Peter’s opinion to show whose opinion we are referring to:

In Maria’s opinion*, we paid too much.*

We often introduce ideas, especially in writing, with the phrase in my opinion:

In my opinion*, there are too many cars on the road with just one person in them.*
Not: ~~On my opinion/To my opinion/According to me/In my point of view~~

warning

We don’t use in my opinion and I think together:

In my opinion*, she’s wasting her time.*
Not: ~~In my opinion I think she’s wasting her time~~.

The phrases It is my opinion that … and I am of the opinion that … are more formal:

It is my opinion that everyone should have free healthcare.
I am of the opinion that the Prime Minister should resign.