Let's learn about "왜 그 생각을 못 했지"

왜 그 생각을 못 했지 : Why didn't I think of that?

[other expressions]

- 왜 그 생각을 못 했나 (to younger people or friends)

- 왜 그 생각을 못 했지 (to younger people or friends)

- 왜 그 생각을 못 했는데 (to younger people or friends)

- 왜 그 생각을 못 했을까 (to younger people or friends)

- 왜 그 생각을 못 했지요 (honourific by ‘-요’)

- 왜 그 생각을 못 했을까요 (honourific by ‘-요’)

[explanations]

* 왜 : why

* 그 : that

* 생각 : thinking

* -을 : a particle makes 뭐 objective after a word ends in a vowel

* 못 : this equal to "not" in English

* 하다 : do

* 했다 : past tense of 하다 by '-었-'

* a verb + -나 / -지 / -는데 / -지요 / -을까요 : 말하는 사람이 원했던 것을 말하며 원하는 대로 되지 않은 아쉬움을 나타내는 종결 어미(a sentence-final ending suffix used to indicate the speaker's regret that something did not turn out the way he/she wanted)

* a verb + -나 / -지 / -는데 / -을까 : a non-honourific descriptive verb ending suffix has an nuance of question

* a verb +  -지? / -을까 + -요 : an honourific verb ending suffix