A bract is a modified leaf associated with a flower's reproductive structure. Its primary function is to protect the flower bud during development. Bracts are often green and leaf-like but can also be colorful (like in poinsettia or bougainvillea) to attract pollinators. They do not protect terminal buds, axillary buds (those are protected by bud scales), or specifically the calyx (which itself protects the inner flower parts).