Plain and spartan both refer to the quality of something that is simple or spare and without any enhancements that provide pleasure, comfort, or ease. Plain suggests something basic, simple, and consisting only of what’s necessary, without pretention or embellishment (a plain room; a plain diet; plain packaging). Spartan suggests a stark simplicity of lifestyle, frugal and minimal to the point of harshness (a spartan diet; spartan conditions). The militarist society of Sparta in ancient Greece, whence we get this adjective, was renowned for its rigorous discipline in every aspect of life. Spartan is often used to describe rooms and furnishings (a spartan room; spartan accommodations).