modified leaf. usually growing just below the flower petals. Sometimes more prominent than and mistaken for the actual flower petals (e.g.. in Comus spp.).
Merriam-Webster Online Dictionary
bract (noun)1.
a leaf from the axil of which a flower or floral axis arises
2.
a leaf borne on a floral axis , especially one subtending a flower or flower cluster
bract (Wikipedia)
Papery (upper) and leafy bracts on hay rattle (Rhinanthus minor). All the "leaves" in this image are bracts.
In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are often (but not always) different from foliage leaves. They may be smaller, larger, or of a different color, shape, or texture. Typically, they also look different from the parts of the flower, such as the petals or sepals. The state of having bracts is referred to as bracteate or bracteolate, and conversely the state of lacking them is referred to as ebracteate and ebracteolate, without bracts.