nonsolid

Nonsolid is an adjective used to describe materials or objects that do not exhibit the properties of a solid. In everyday language it implies a lack of fixed shape and rigidity, and an ability to flow or change shape to fit a container. The term is broad and imprecise, and it is often used as a general descriptor rather than a formal classification.

In scientific contexts, nonsolid is not a standard category. Scientists typically distinguish among specific states of matter—solids, liquids, gases, and plasmas—or between solid-like and fluid-like behavior in soft matter. The label nonsolid may be used informally to refer to liquids, gases, plasmas, and other fluids, or to materials that do not act as rigid solids under given conditions. It can also appear in discussions of rheology and viscoelasticity, where materials exhibit both solid- and liquid-like responses.

Examples of nonsolid states include water in the liquid state, steam or air in the gaseous state, and plasmas found in stars and certain laboratory conditions. Molten metals are liquids and thus nonsolid. Some complex fluids, gels, and foams can display non-solid flow under stress, but researchers usually describe them with more specific terms reflecting their behavior.

Etymology and usage: nonsolid comes from the prefix non- with solid, and is most often encountered in informal or descriptive prose rather than formal technical writing. See also states of matter, rheology, and soft matter.