Puolikiinteän

Puolikiinteän is a Finnish term that translates to "semi-solid" in English. It describes a state of matter that is neither fully solid nor fully liquid, exhibiting properties of both. In a puolikiinteän substance, the particles are not arranged in a rigid, ordered structure like in a solid, nor are they completely free to move past each other like in a liquid. Instead, they are able to flow over long timescales but resist flow over short timescales.

This intermediate state is often characterized by a yield stress, meaning that a certain amount of force must be applied before the substance begins to deform or flow. Below this yield stress, the material behaves like a solid. Once the yield stress is exceeded, it exhibits viscous flow, similar to a liquid. Examples of puolikiinteän substances include toothpaste, ketchup, mayonnaise, yogurt, and mud. These substances can hold their shape to some extent but will spread or drip when a sufficient force is applied. The rheological properties of puolikiinteän materials are complex and are studied in the field of rheology, which deals with the study of the flow of matter.