A fountain pen is a nib pen that, unlike its predecessor the dip pen, contains an internal reservoir of water-based liquid ink. The pen draws ink from the reservoir through a feed to the nib and deposits it on paper via a combination of gravity and capillary action.
Filling the reservoir with ink may be achieved manually (via the use of a Pasteur pipette or syringe), or via an internal filling mechanism which creates suction (for example, through a piston mechanism) to transfer ink directly through the nib into the reservoir. Some pens employ removable reservoirs in the form of pre-filled ink cartridges. A fountain pen needs little or no pressure to write.