sepal

One of the outermost whorl of flower parts, collectively termed the calyx. Usually green, free, or sometimes fused together, they protect the flower in bud. They sometimes assume other roles, such as becoming enlarged and brightly coloured, and acting as petals.

A sepal is an individual unit of the calyx of a flower. The term tepal is usually applied when the petals and sepals are not differentiated. When the flower is in bud, the sepals enclose and protect the more delicate floral parts within.

The number of sepals in a flower (called merosity) is indicative of the plant's classification: eudicots having typically four or five sepals and monocots and palaeodicots having three, or some multiple of three, sepals.

There exists considerable variation in form of the sepals among the flowering plants. Often the sepals are much reduced, appearing somewhat awn-like, or as scales, teeth, or ridges. In some flowers, the sepals are fused towards the base, forming a calyx tube.