squircular

Squircular is an adjective describing shapes or curves that blend characteristics of a square and a circle. The term is a variant of squircle, a portmanteau of square and circle used in mathematics and design to denote a curve or region that interpolates between circular and square geometry.

In mathematical modeling, a common representation of a squircular shape is a kind of superellipse. For example, the equation |x/a|^n + |y/b|^n = 1 with a = b and n around 4 produces a symmetric curve that is circular near the corners and flatter along the sides, yielding a rounded-square appearance. Other parametrizations, such as x^4 + y^4 ≤ r^4, yield similar results. The essential feature is a controllable transition between round and square forms, allowing a shape that sits between the two extremes.

Squircular shapes are widely used in design and graphics due to their balance between the regularity of a square and the softness of a circle. They are common in user interface elements, icons, logos, and fonts, where rounded corners provide a visually appealing compromise that remains compatible with grid layouts and scalable rendering.

The term is often used interchangeably with squircle, though some contexts differentiate the noun (the shape) from the adjective (squircular). The concept belongs to the broader family of superellipses and related rounded-square forms used in digital imaging, graphic design, and geometric modeling. See also squircle, superellipse, rounded rectangle.