What is the name of feather parts?

The feather of a bird consists of a central, hollow shaft called *rachis*, which runs along the length of the feather and provides strength. The rachis is connected to a series of *barbules*, which are flat, thin structures that resemble tiny hooks. The barbules are arranged in a row on each side of the rachis, and each barbule is further attached to other barbules by even smaller structures called *barbicels*. The interlocking of the barbules and barbicels creates the interlocking system of the feather, which provides strength and aerodynamic efficiency during flight. At the base of the feather, there is the *calamus*, which is the hollow, cylindrical base that attaches the feather to the bird's skin through the feather follicle. The fluffier part of the feather at its base is called the *hypenellum*.