Define and explain the term anisotropy.

Explanation

**Step-by-Step Text Solution:**

1. **Definition of Anisotropy**: Anisotropy refers to the property of a material where its physical properties vary when measured in different directions. This means that the material exhibits different characteristics depending on the orientation from which it is observed.

2. **Types of Solids**: There are two main types of solids: crystalline and amorphous. Crystalline solids are known to be anisotropic, while amorphous solids are generally isotropic.

3. **Characteristics of Crystalline Solids**: In crystalline solids, the arrangement of particles (atoms, ions, or molecules) is highly ordered and extends in a regular pattern. This ordered structure leads to variations in physical properties such as electrical resistance, thermal conductivity, and refractive index when measured along different crystallographic directions.

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