Which mathematical term corresponds to the vocabulary 'closed figure'?

The term that corresponds to the vocabulary 'closed figure' is indeed a circle. A closed figure is defined as a shape where all the endpoints of the figure are connected, creating a continuous outline without any openings. A circle perfectly embodies this concept as it is defined by all points equidistant from a central point, forming a complete and unbroken curve.

While the other options, such as polygon, square, and rectangle, also describe closed figures, the question specifically may have been interpreted differently. A polygon, for instance, encompasses closed figures formed by straight lines. A square and a rectangle are specific types of polygons that consist of straight sides. Therefore, all mentioned shapes can be considered closed figures, but the circle represents a unique case of closure through curvature rather than straight edges, which may have led to confusion in interpreting the question.