Correct spelling, explanation: opinion is a noun that originates from Old French opinion and from Latin opinionem. As you can see, it’s a loanword. It means the spelling depends on the construction of the words from which this one comes. You should bear that in mind when writing down this verb. Opinion is the only correct version and oppinion is just a mistake.

Incorrect spelling, explanation: in the English language, two vowels are often found next to each other. However, this is not the case with the word opinion. We shouldn’t add another -p consonant to this noun, that’s why oppinion isn’t correct. Remember that opinion is the only right version – even the etymology indicates so.

Definition of opinion:
noun, a view, judgment, or appraisal formed in the mind about a particular matter
Public opinion can force the government into action.
I’ve recently changed my opinion of Mark.

Collocations with opinion:
Some most commonly used collocations include: second opinion and public opinion.
I’m going to go to another doctor to get a second opinion.
A revolution in public opinion occurred during the late 1950s and early 1960s on issues of civil rights.

Incorrect spelling