A quill is a large feather, usually taken from the wing or tail of a bird like a goose or swan, that was used for centuries as a writing pen. Writers would sharpen the hollow end of the feather into a point, dip it in ink, and use it to write on paper or parchment. Before metal pens and ballpoint pens were invented, quills were the main writing tool in Europe and America. The Declaration of Independence was signed with quill pens in 1776.

Using a quill required real skill: you had to hold it at just the right angle, dip it frequently without dripping, and periodically trim the tip to keep it sharp. Many great works of literature, from Shakespeare's plays to Jane Austen's novels, were written with quill and ink.

The word also refers to the sharp, needle-like spines of a porcupine. These quills are actually modified hairs that can detach and stick into predators when the porcupine feels threatened. Unlike bird feathers, porcupine quills are stiff, barbed, and designed for defense rather than flight.

Today, people might use “quill” poetically to mean any pen or the act of writing itself, especially when referring to authors and their craft.