adjective
Definition: Simple and without any decoration; ordinary or not special in appearance.
Example: She wore a plain dress to the party.
adverb
Definition: In a clear and simple way, without any confusion or complexity.
Example: She explained the rules of the game plain so everyone could understand.
noun
Definition: A large, flat area of land that is mostly level and often has few or no trees.
Example: The vast plain stretched out before us, covered in golden grass.