na-adjective, noun
Describes something that is not complex, easy to understand, or straightforward. Also used for a person who is simple-minded or naive, often with a negative or pitying nuance.
Antonyms: 複雑
この問題は単純だからすぐ解ける。
This problem is simple, so I can solve it right away.
彼は単純な性格で、すぐ人を信じてしまう。
He has a simple-minded personality and trusts people too easily.