apparatus
an apparatus has a specific purpose and it's complex, whereas an instrument is just a tool, like a hammer. https://gyazo.com/5da125383072da90e903e8e8513e3925
〖集合的に〗(科学・医療などの)器具一式, 装置 (!数えるときはa piece of ~) ; C(1つの)器具, 装置
〖通例単数形で〗(政治的な)機構, 組織
ORIGIN