(continue) 2. When will the sentence that doesn't use '-다' or '-요' - About -다 => - 다 is an attachement that makes a verb into a basic verb. For the further explnation, I have already mentioned it above. Please check '1. -니다 (X) / -다 (O)' above. - About - 요 => '-요' is usually used in a conversation. -요 changes a sentence into a conversational sentence. Which means, it mostly not used in a writing sentences. => Plus, -요 is an attachment that just adds up at the last at the whole sentence to end the sentence. So it's function is to 'close' the sentence in a polite way and nothing else. So there is more cases that 'use' -요 in a sentence rather than 'not to use' -요 in a sentence. ^^;; - When is the time that -요 / - 다 is not used in a sentence. => There are so many cases that - 요 and - 다 is not used in a sentence. So to make it simple, if you can understand the usages that I have written above, about the -요 and -다, that will give you an answer to this question. Since all other cases that doesn't fits those explanations will all be applied to 'not using - 요 and - 다' case. ^^;; * About -는지 : I am not sure what level of Korean are you studying, but if you are in Beginner, You can just drop it. Since it is an intermediate grammar so learning it will only make you more confusing right now. So, you can take time and learn things slowly one by one.

[Example] I don't know if this is right. -> 나는 이것이 맞는지 모릅니다. I am not sure if this is expensive or not. -> 나는 이것이 비싼지 아닌지 확실하지 않다.

Hello. : ) I hope my answers can be a help a bit. :3 First of all, the question you are asking are covering from beginner - intermediate course, and especially on grammar. So my explanations might be a little bit difficult. But I will try my best to make it simple. So let's start. :) To 'conjugate' the verb, there is a grammar term that is called 'Attachment / Endings' in Korean. Those two have different names but basically, they are meaning the same thing. These "Attachment / Ending" is attached to the verb and conjugate verbs into a conversational forms. It is just a theory, so I will explain these attachments and endings one by one. So, the ones that you've asked are " -다 / -는지" and '-니다 / -요' are the things that you already know. But there is a slight thing that I should point out before I explain things that you've asked. 1. - 다 (O) / - 니다 (X) '-니다' is not a term to conjugate a verb. There is a '-다' in Korean, and it is a ending form to make a 'basic verb' like 'to-' is in English. So, to give you an example... In Korean : 가다 = In English : to go In Korean : 먹다 = In English : to eat So, '-다' is an ending as It is basically showing a verb as a basic form. When you conjugate, you need to delete '-다' and add endings and attachments to make it into a sentence.

(continue) For example... 가다 (= to go) => 가요 ( - 다 is deleted and the ending -요 is attached ) Just like this, '-다' is always deleted when you are making a sentence when you want to conjugate verb in a conversations. (* The only exception is when you are writing, but when you speak, -다 itself is almostly never used. There is a one called -습니다 / -ㅂ니다 but it is another story and it is nothing to do with the attachment -다) * I will attach anther answer for -는지 in the second reply. If you have any questions related to - 다, please ask me the questions below. Or, I am also working as a community tutor in Itaki, so you can sign up my course also. Hope it can be a help. : )

I have to say sorry. ^^;; Because my answers above were little out of sense..;;; It didn't fit your questions right. I should have read the questions more specifically. :3 So, what you were asking about was... 1. How to conjugate verbs in Korean. 2. When will the sentence not end in -다 / 요. (* -니다 is not a right term so I changed it into -다) 1. How to conjugate verbs in Korean. - As like the replying above (please refer '1. -니다 (X) / - 다(O) above), Korean verbs conjugate form is like this. * Verb - 다 + (Attachments / Endings that you want to use) Ex) 가다 (to go) -> 가요 : 가다 - 다 + 요 = 가요. (continue)