trefoil - Architecture

A member of either of two groups of plants belonging to the pea family, Leguminosae. Genus Trifolium comprises yellow-flowered species of clovers. Genus Lotus includes a widely distributed group of annual or perennial herbs, occurring in Europe, Asia, Africa, North America, and Australia; leaves divided into five leaflets; pea-like flowers, small, often yellow or reddish-coloured; pods long, many-seeded.

Architecture

Trefoil (from Latin trifolium, three-leaved plant, French trèfle, German Dreiblatt and Dreiblattbogen) is a term in Gothic architecture given to the ornamental foliation or cusping introduced in the heads of window-lights, tracery, panellings, etc., in which the center takes the form of a three-lobed leaf (formed from three partially-overlapping circles). Two forms of this are shown below:

A dove, symbolic of the Holy Spirit, is sometimes depicted within the outlined form of the trefoil combined with a triangle.