"Everybody should drink plenty of fluids"
A liquid or fluid was one of the four fundamental states of matter. It could be characterized as a fluid of neutrally-charged atoms that were held together by intermolecular bonding. A liquid had a fixed volume, but its shape was determined by its container.
The Founders' natural state was that of a liquid. In 2371, the Romulans were able to distinguish individual life signs from orbit of the Founders' homeworld via sensors, while they were in a liquid state. It was later determined that these sensor reading were false, and that the planet was deserted. (DS9: "The Die is Cast")
|Phases of matter|
|Gas • Liquid • Plasma • Solid|