The scotia (from the Latin scotia and this from the ancient Greek σκοτία, "darkness", "shadow"), also scota or troquilo, is a concave molding, composed of two curves of different radii, the lower arch normally being the largest.

Its name comes from the fact that when it was present on the Greek base of the columns "Column (architecture)") of the Ionic order, it produced a pronounced effect of shadows and lights that transmitted expressiveness and movement.

The concave molding whose profile is semicircular is called half-round.