Yes. It's the impersonal "Plain form" (past tense in this case).
It can be used in speech:
• when musing to oneself.
• as casual statements to friends or people younger than you. Usually used as an announcement or as exclamation (reaction).
• in public, when addressing a large group of people when speaker doesn't know who the audience is.
Ah thank you! I've been learning Korean for a while now and I never knew that the plain form could be spoken! :) I'm gonna go and look into it a bit more now online. Just one question, what do you mean by "musing to oneself"? Is that different from just talking about yourself in general?
(1) "죽다" (intransitive verb) is really a colloquial word for "to die", not usually referring to people = to stop living
"죽었다" (죽다, past tense) = died.
(2) 죽어 있다 (adjectival verb) means "dead" = no longer alive <- a resulting state of 죽다
(3) 죽다 = to die || 죽어 있다 = (be) dead.
• 그는 죽는다 = he dies = he stops living (죽다 present tense)
그는 죽었다 = he died = he stopped living (죽다 past tense)
• 그는 죽어 있는다= he is dead = he is no longer alive [ *있는다 = being, present state ]
[Naver dict.] = lies dead
• 그는 죽어 있었다 = he was dead = he was no longer alive [ *있었다 = been/done, past state ]
[Naver dict.] = found dead
(4) In common usage:
죽었다 "died" (past tense) is also used (by inference) to mean is/are dead ( describing the present state)
그는 죽었다 = he died --> he is dead.
Edited March 2020