다

a verb's bare dictionary form

The plain, undressed ending every Korean verb wears in the dictionary — 사다, 자다, 보다, 찾다. Because it is not aimed at any listener, speakers also use it to blurt something to themselves or to narrate: 역사적인 순간이다 is "this is a historic moment", 에라 모르겠다 is "ah, whatever". It is the same form that feeds the very common chains -다 보니까 ("as I kept doing it, it turned out that…") and -다 보면 ("if you keep doing it, eventually…"), heard here in 하다 보니까 and 가다 보면. Said straight at another person it sounds abrupt, so in conversation it stays mostly self-directed.

Register: plain / self-directed