Watashi wa sensei to iu wake ga nai Watashi wa sensei (da) to iu wake ga nai my opinion/We don't use these sentences much. Whenever you use "wake", "koto" could be used too? If yes, with the same meaning? Watashi wa sensei (da) to iu wake desu Watashi wa sensei (da) to iu koto desu These sentence's meaning were same.(this is answer for your question） I understood you.But these sentences are not suitable. Kare wa sensei (da) to iu wake desu Kare wa sensei (da) to iu koto desu were better. Because when we want to explained someone(something) to someone(←sorry my explain is not good. Do you understand?) we use both sentences [(da) to iu wake]and[(da) to iu koto]. Watashi wa sensei de iru koto ni wa ikanai Watashi wa sensei (da) to iu koto ni wa ikanai If change these sentences below Kare wa sensei de iru koto ni wa ikanai Kare wa sensei (da) to iu koto ni wa ikanai My opinion / maybe same, but I think we don't use these sentences. Kare wa sensei de iru koto ni wa ikanai →Kare wa sensei de iru wake ni wa ikanai 　　is better. This means [ He can't be teacher any more.] like that. Kare wa sensei (da) to iu koto ni wa ikanai →Kare wa sensei (da) to iu wake niwa ikanai 　is useful. This means [ He can't be teacher any more.] like that. Watashi wa sensei (da) to iu koto ka. Watashi wa sensei (da) to iu wake ka If change these sentences below Kare wa sensei (da) to iu koto ka. Kare wa sensei (da) to iu wake ka These meanings are same. I think we used [to iu wake][koto ka] at the end of a sentence, just speaking. When we can understand some reason or course, we use these sentences.