A sepal (from Latin separatus "separate" + petalum "petal") is a part of the flower of flowering plants. Sepals in a "typical" flower are green and lie under the more conspicuous petals. As a collective unit the sepals are called the calyx, and the collection of petals is called the corolla. Together, these two structures are known as the perianth of the flower. The petals and sepals are usually differentiated into colorful petals and green sepals. 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.