花瓣是花冠的一个组成部分。它是花被的内部组成部分，是花无性的一个组成部分。花被的内部一般分花瓣和花萼，但有些花的花瓣和花萼非常相似而难以分辨，甚至于形态上完全相同，这时它们可称为花被片，或统称为花瓣。典型的花的花瓣的颜色和形状非常鲜艳，它们环绕植物的生殖器官。花瓣的数目往往是花的分类的一个标志：双子叶植物一般有四或五枚花瓣，而单子叶植物一般有三枚或三的倍数枚花瓣。

被子植物的花的花瓣的形状和颜色非常多，有些花的花瓣在其基部连在一起组成一个花筒，有些花的整个花被组成一个环绕着雌蕊群的花杯。

有些植物的花瓣退化了，或根本消失了。比如许多草就是这样的。

Petals are modified leaves that surround the reproductive parts of flowers. They are often brightly colored or unusually shaped to attract pollinators. Together, all of the petals of a flower are called a corolla. Petals are usually accompanied by another set of special leaves called sepals, that collectively form the calyx and lie just beneath the corolla. The calyx and the corolla together make up the perianth. When the petals and sepals of a flower are difficult to distinguish, they are collectively called tepals. Examples of plants in which the term tepal is appropriate include genera such as Aloe and Tulipa. Conversely, genera such as Rosa and Phaseolus have well-distinguished sepals and petals. When the undifferentiated tepals resemble petals, they are referred to as "petaloid", as in petaloid monocots, orders of monocots with brightly coloured tepals. Since they include Liliales, an alternative name is lilioid monocots.