What do you call a plane figure with four equal sides and four right angles?

A plane figure with four equal sides and four right angles is specifically categorized as a square. The characteristics of a square include not only having four equal length sides but also that each internal angle measures 90 degrees, which is a defining trait of right angles. A square is a specific type of rectangle since all angles are right angles, but it is distinct because of its equal side lengths.

While a rectangle also has right angles, it does not require the sides to be equal, allowing for varying lengths. A rhombus, on the other hand, has equal sides but does not necessarily have right angles; in fact, its angles can be acute or obtuse. A quadrilateral is a broader term that encompasses any four-sided figure, including squares, rectangles, and rhombuses, without specifying side lengths or angles. Therefore, referring to this figure as a square is precise as it fulfills all conditions specified in the question.