A fountain pen is a writing instrument that uses a nib to apply liquid ink to a surface, typically paper. It features a refillable ink reservoir, which allows for longer writing sessions without the need for constant replacements. The design often incorporates elegant materials such as metal or high-quality plastic, and can have elaborate patterns or finishes. Fountain pens can provide a smooth and fluid writing experience, making them a favored choice for calligraphy and important documents. The nib can come in various sizes, influencing the thickness of the line produced.