The so-called rigidity means that two objects will not deform when they collide, so two rigid bodies will not occupy the same space. Particles and atoms are such substances.

A strong character; Strong temperament: what a man should have. Hard and unchangeable (as opposed to' flexible '):~ object. Unable to change or adapt (as opposed to "flexibility"): ~ indicator.

Technical terms of modern furniture manufacturing. It is the ability of furniture to resist deformation under static load. In industry, mechanical stiffness is also an important index of machinery.

Mathematically, rigid equation refers to a differential equation, and its numerical analysis solution will be stable only when the time interval is small, and its solution will be unstable as long as the time interval is slightly larger. It is difficult to define exactly which differential equations are rigid, but the general idea is that the solution of this equation contains rapidly changing parts.