Allotropes of Sulfur: Sulfur can exist in multiple crystalline forms, known as allotropes, with different physical and chemical properties. The most common allotropes include $\alpha$-sulfur, $\beta$-sulfur, and $\gamma$-sulfur.
Crystalline Structure: The arrangement of atoms in a solid material, such as a crystal, that determines its physical and chemical properties. The crystalline structure of $\beta$-sulfur is different from other allotropes of sulfur.
Phase Transitions: The changes in the physical state of a substance, such as the transition from solid to liquid or liquid to gas. $\beta$-sulfur undergoes phase transitions at specific temperatures and pressures.