A reservoir pen is a type of writing instrument that has a built-in ink container or reservoir, allowing for continuous ink flow while writing. There are various synonyms for the term "reservoir pen," including fountain pen, ink pen, dipping pen, and quill pen. The fountain pen is a type of reservoir pen that uses a mechanism to transfer ink onto the paper. An ink pen also has a reservoir for ink but is typically smaller than a fountain pen and can be disposable. Dipping pens are similar to fountain pens but require frequent dipping in ink during use. Quill pens, on the other hand, are made from bird feathers and were commonly used for writing in the past.