그것은 왜지? - Why? 나는 왠지/왜인지 모르겠다. I don't know why. 너는 왜인지/왠지 아니? Do you know why? 왜인지가 궁금하다. I wonder why. They are different in usage. When you use '왜지', you have to finish your sentence, because '왜지' is a verb. When you use '왜인지/왠지' you need a verb, because they are not a verb.

다름 사이에 '왠지'하고 '왜지' 있어요? I think I asked this question right? - No, it needs correction. Correction: Is there a difference between '왠지' and '왜지'? '왠지'하고 '왜지' 사이에 차이가 있어요? or '왠지'와 '왜지'가 다른가요? I know 왠지 is short for 왜인지 and means something like "I don't know why but..." Does 왜지 have the same meaning? - The word "왜(이)지?" means "why is it (that)?" Sometimes, interrogative adverb 왜(why) can be used as interrogative noun. The interrogative noun 왜 can be replaced with the noun phrase "어떤/무슨 이유/까닭 (what reason/cause) or "무엇을 하려고(what for)". And It is ended in a.vowel 'ㅐ', so the letter '이' can be left.out when the predicative case particle or copula '-이다' follows it. Consider the following examples. Why is it (that ...)? 왜(-이)냐?, 왜냐? 왜(-이)지?, 왜지? 왜지요? 왜죠? 왜일까? 왤까? 왜냐고 하면, 왜냐 하면, 왜냐면, (If you ask) why it is (that), or (it is) because 왜인지 (몰라도/모르게), 왜(-이)-ㄴ지, 왠지 (몰라도/모르게), I don't know why (it is), but or without knowing why (it is)