o·pin·ion

– noun
1. a belief or judgment that rests on grounds insufficient to produce complete certainty.
2. a personal view, attitude, or appraisal.
3. the formal expression of a professional judgment.
4. the formal statement by a judge or court of the reasoning and the principles of law used in reaching a decision of a case.
5. a judgment or estimate of a person or thing with respect to character, merit, etc..
6. a favorable estimate; esteem.

es·ti·mate

– verb
1. to form an approximate judgment or opinion regarding the worth, amount, size, weight, etc., of; calculate approximately.
2. to form an opinion of; judge.
3. guess.
–noun
4. an approximate judgment or calculation, as of the value, amount, time, size, or weight of something.
5. a judgment or opinion, as of the qualities of a person or thing.
6. a statement of the approximate charge for work to be done, submitted by a person or business firm ready to undertake the work.

cal·cu·late

– verb
1. to determine or ascertain by mathematical methods; compute.
2. to determine by reasoning, common sense, or practical experience; estimate; evaluate; gauge.
3. to make suitable or fit for a purpose; adapt.
4. a. to think; guess.
b. to intend; plan.