Saccheri quadrilateral

A Saccheri quadrilateral is a type of special, four-sided shape that is used in mathematics to help us understand how different shapes can be related. It looks like a square with two of its sides bent inwards. Imagine taking four toothpicks and putting them together so that you have a square. Now, take two of the toothpicks and curve them inwards, so that they almost make a triangle shape with the other two toothpicks. You've just made a Saccheri quadrilateral.
Saccheri quadrilaterals help us understand the relationships between different shapes, like squares and triangles. For example, if we have a Saccheri quadrilateral, no matter how big or small its sides are, we know that the angles opposite the curved sides will always add up to the same number.