opin- +

1. To speak one's opinion without fear or hesitation.
2. To expect, to believe, or to suppose.
3. To express an opinion, or to express something as your opinion.

Having stated or expressed an opinion or belief.

When someone holds or expresses an opinion.

Holding and stating something as one’s opinion.

1. The view someone takes about an issue; especially, when it is based solely on personal judgment: "In my opinion, the study of vocabulary is essential to a superior education."
2. A view regarding the worth of someone or something: "For some reason, they don't seem to have a very good opinion of what I am striving to accomplish."
3. An expert assessment of something: "She told the dentist that she wanted a second opinion before he started to pull out so many teeth."
4. The view or views held by most people or by a large number of people: "Political polls are used to establish trends and other political opinions."
5. A belief or conclusion held with confidence but not substantiated by positive knowledge or proof.
6. In law, a conclusion drawn from the observation of the facts.

Capable of having an opinion or thought about something or someone.

1. Being obstinate or stubbornly persistent in one's viewpoint.
2. Always ready to express opinions and tending to hold to them stubbornly, unreasonably dismissing other people's views.
3. Holding stubbornly and often unreasonably to one's own opinions; conceitedly dogmatic.

Descriptive of someone who unduly adheres to his/her own opinions or to preconceived notions.

The process of holding stubbornly and often unreasonably to one's own opinions.