Oblúk

Oblúk is the Slovak and Czech term for an arc, curve, or arch. In general use, it denotes a smoothly curved form connecting two endpoints, and it can refer to both geometric and architectural contexts. In Slovak, the plural is oblúky, and in Czech it is oblouky.

In mathematics, an oblúk is the portion of a circle’s circumference between two points. It is defined by the circle’s center and radius and by the central angle that subtends the arc. If the radius is r and the central angle is θ (in radians), the length of the arc is s = rθ. The corresponding sector area is (1/2) r^2 θ. An arc can be described by its endpoints and a point on the arc, which determines the circle containing it.

In architecture and construction, an oblúk refers to a curved element that spans an opening, such as a doorway or window. Architectural oblúky provide support and define the building’s silhouette. Common forms include semicircular (round) arches, segmental arches, pointed arches, and other curved profiles, each influencing load distribution and stylistic character.

The term is also used more loosely to describe any curved line or outline in design, nature, or engineering, such as the bend of a river or a road. Etymologically, oblúk derives from the common Slavic noun for a curved shape, and it remains a basic, widely understood term in Slovak and Czech language contexts.