sepal

n. individual leaf of the calyx of a flower (Botany)

A sepal (from Latin separatus "separate" + petalum "petal") is a part of the flower of angiosperms or flower plants. Sepals in a "typical" flower are green and lie under the more conspicuous petals. As a collective unit the sepals are called the of a flower.The calyx is part of the perianth of the flower which is composed of the sepals collectively called the calyx, which is the outer part of the flower with the inner part of the perianth composed of the petals, which are collectively called the corolla. The petals and sepals are usually differentiated into colorful petals and green sepals. But many flowers have colorful sepals and lack petals or the sepals and petals look similar and are often called tepals. The term tepal is usually applied when the petals and sepals are not differentiated and look similar or the petals are absent and the sepals are colorful. When the flower is in bud, the sepals enclose and protect the more delicate floral parts within. Morphologically they are modified leaves.
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Noun
1. one of the green parts that form the calyx of a flower
(hypernym) floral leaf
(part-holonym) calyx

n. sepal

(n.)
A leaf or division of the calyx.