opinion is the specialized manifestation about a certain subject.
In legal terms, the opinion is the understanding issued by a jurist with authority in a given matter. It is a legal document requested to support a court decision.
The verb to seem, in its origin, means what looks like or appearance of something. As a noun, an opinion corresponds to what, according to the technical assessment, seems to be adequate. That is, it looks right.
Giving an opinion is to convey more than an opinion, it is to express oneself in an informed way. Its objective is to explain the subject, clearly and precisely, to another party whose technical knowledge is not the same as that of the referee.
Technical opinion is the professional evaluation of something. In the health area it also occurs, being called medical opinion or psychological opinion, depending on the issue and the professional issuing the opinion.
As a legal opinion, the document can be issued by a public agency, such as the Public Ministry, for example. It can also be issued by private lawyers, such as a lawyer or legal advisor. The legal opinions that support the opinion must have legal bases, based on jurisprudence or even of a doctrinal nature.