ringjoonilised

Ringjoonilised is an Estonian term meaning ring-shaped or annular. It is used to describe objects, figures, or patterns that resemble a circular band, such as washers, bracelets, or geometric regions that form a ring around a central void. The term is common in geometry, design, and industrial contexts.

In geometry, a ringjooniline figure refers to an annulus: the region between two concentric circles with inner radius r and outer radius R. Its area is π(R² − r²), and its boundary consists of two circles of radii R and r. If the inner radius is zero, the ringjooniline becomes a disk; if the outer and inner radii are equal, the figure degenerates to a circle. This concept helps distinguish between solid circular shapes and hollow circular bands.

In practical contexts, ringjoonilised shapes appear in mechanical components like washers, seals, and gaskets, as well as in jewelry design and architectural ornamentation. They also appear in biology and art, where circular bands create emphasis, rhythm, or negative space.

The term is used primarily in Estonian-language texts, with English equivalents including ring-shaped, annular, or annulus-related expressions. Exact usage may vary by discipline, but the core idea remains: a form defined by a circular band around a central void.