to have confidence in the truth, the existence, or the reliability of something, although without absolute proof that one is right in doing so: Only if one believes in something can one act purposefully.
to have confidence or faith in the truth of (a positive assertion, story, etc.); give credence to.
to have confidence in the assertions of (a person).
to have a conviction that (a person or thing) is, has been, or will be engaged in a given action or involved in a given situation: The fugitive is believed to be headed for the Mexican border.
to suppose or assume; understand (usually followed by a noun clause): I believe that he has left town.