Public opinion refers to the opinions or views of people in a community or country on issues of public interest or concern. Such issues may deal with any subject that is open to differing beliefs and attitudes. For example, it is a matter of opinion whether the nations of the earth should attempt to cooperate in some sort of international organization, and, if so, what form this organization should take. In matters of opinion, reasonable people may hold widely different viewpoints.

On the other hand, it is no longer considered to be merely a matter of opinion that the earth is a sphere rotating on an axis and revolving in an orbit around the sun. It is a matter of fact, which can be demonstrated and about which reasonable people do not differ.

When a problem affects a number of people, they will discuss it and argue about it. These activities help develop a common opinion, or consensus. When discussion is open or public, these matters are public opinions. Public opinion, in this sense, varies widely in its character and content. Public opinion may be merely the variety of individual opinions in the early stages of discussion, when issues are not sharply defined and people are not well informed about them. At other times, the opinions of many individuals may become similar enough to form a majority opinion or even a consensus, which determines the kind of action a group will take. A vote decided by the majority gives structure to the group opinion and makes it lawful.

There is no definite way in which public opinion affects the decision-making process of government leaders and groups. Elections of political leaders are one important way the public can express its judgment about a candidate. However, the process of shaping government policy is often slow and uneven. Expressions of opinion may influence politicians. But such expressions also may be disregarded because public opinion lasts only a short time, is emotionally charged, and usually represents the more visible and vocal portion of the population. The balance of the population, often called the silent majority, does not express its views as regularly or as visibly.

Nevertheless, one of the major concerns of a democratic society is to determine the extent and significance of the opinions held by individuals and groups. The most common technique today, the public opinion poll, is used to survey the opinions of a sample of the population. The accuracy of the results depends on the knowledge and skill of the pollsters in selecting the sample and in developing good interview questions. There is always some margin for error in the results.