Given the task definition and input, reply with output. In this task, we ask you to rewrite a sentence in simple English without changing its general meaning. Essentially, you want to make the sentence easier to read by using simpler words, utilizing more straightforward sentence structures, and omitting non-essential information etc.

A crystal or crystalline solid is a solid material whose constituents ( such as atoms , molecules , or ions ) are arranged in a highly ordered microscopic structure , forming a crystal lattice that extends in all directions .

A crystal is a solid whose molecules ( or atoms ) are arranged in a repeating pattern .