Allotropy is existence of a chemical element in two or more different states. When an element exists in more than one physical state, they are said to be allotropes.
Many different substances exhibits allotropy and it largely impacts their physical state.
Carbon has two main allotropes; graphite and diamond. Graphite is a soft substance and can easily be broken. Diamond is the hardest natural substance that is known.
A sulfur with a glassy luster and another with a dull earthy luster signifies two sulfur allotropes.