A crystalline material, including a crystalline polymer, possesses a highly ordered, three-dimensional arrangement of atoms or molecules in a repeating lattice structure. This ordered arrangement leads to specific properties like sharp melting points, anisotropy (direction-dependent properties), and often increased strength and stiffness. In polymers, crystallinity refers to the extent to which the polymer chains are arranged in this ordered manner.

结晶材料（包括结晶聚合物）在重复的晶格结构中具有高度有序的三维原子或分子排列。这种有序排列导致特定的性质，如明确的熔点、各向异性（取决于方向的性质），并且通常会增加强度和刚度。在聚合物中，结晶度是指聚合物链以这种有序方式排列的程度。