liquid
/ LIK-wid /
Pour water from a bottle into a bowl and it takes the shape of the bowl, filling the bottom and leaving a flat top. It keeps the same amount but happily changes shape. That combination — fixed volume, no fixed shape — is what makes something a liquid.
In a liquid the atoms or molecules stay almost as tightly packed as in a solid, so it is hard to squeeze into a smaller volume, but the bonds between them keep breaking and reforming. Because of that, the particles can slide and tumble past one another, which lets the liquid flow and pour. It is a kind of middle ground: too crowded to fly apart like a gas, too loose to stay rigid like a solid.
This matters because liquids carry, dissolve, and transport almost everything in life and industry — blood, oceans, fuel, molten metal — thanks to their twin gifts of staying dense yet flowing freely. A subtle point often missed is that flowing easily is not the same as being a liquid: honey and tar flow very slowly, and glass barely flows at all, so flow speed is about viscosity, not about whether something counts as liquid.
Water poured into a glass settles into the glass's shape with a flat, level surface, yet you cannot compress that water into half the space — proof that a liquid changes shape freely but guards its volume.
Water takes the glass's shape yet keeps its volume.
A liquid is not just a soft solid: the key difference is that its atoms have no fixed neighbours and keep rearranging, which is why a liquid cannot support its own shape the way a solid can.