I am tired. I want to take a rest.
take a rest 英[teik ə rest] 美[tek e rɛst] [词典] 休息一下; [例句]It'll do you good to take a rest.休息一下对你有好处。
I am exhausted. I want to have a rest.
exhausted 英[ɪgˈzɔ:stɪd] 美[ɪɡˈzɔstɪd] adj. 精疲力竭的; 筋疲力尽的; 耗尽的; 用完的; v. 用尽( exhaust的过去式和过去分词 ); 使非常疲倦; 详尽讨论(或研究); 弄空; [例句]I was perished. No jacket, no torch, wet through, exhausted.我快冻僵了。没有外衣,没有火把,浑身湿透了,筋疲力尽。[其他] 原型: exhaust