What constitutes a seizure under the Fourth Amendment when a police officer approaches an individual and asks a few questions?

In contrast, a seizure "does not occur simply because a police officer approaches an individual and asks a few questions. So long as a reasonable person would feel free `to disregard the police and go about his business,' [citation], the encounter is consensual and no reasonable suspicion [of criminal activity] is required. The encounter will not trigger Fourth Amendment scrutiny unless it loses its consensual nature. . . . `Only when the officer, by means of physical force or show of authority, has in some way restrained the liberty of a citizen may we conclude that a "seizure" has occurred.'" (Florida v. Bostick (1991) 501 U.S. 429, 434 [115 L.Ed.2d 389, 398].)