2026 4th Grade MCA Math Vocabulary Practice Test – Complete Exam Prep

Shapes that have an opening are called open figures. An opening means the boundary doesn’t close all the way, leaving a gap. Think of a circle with a small gap, or a shape like a letter C or a U-shaped outline—the sides don’t form a complete loop. A closed figure, by contrast, has a boundary that completely surrounds the figure with no gaps, like a circle, a square, or a triangle. A polygon is a shape made with straight line segments that connect and form a closed figure, so it doesn’t have openings. A triangle is a simple polygon with three sides and it also closes up to make a complete boundary. So the term that means a shape with an opening is open figure.