다: all 전부: all, no exception 전체: all as a whole 다 sounds somewhat childish and subjective 다 내거야! : They all belong to me! 다 can also mean "almost" 다 왔다: we are almost there 집에 다 와서 사고가 났다: We were almost home when the accident happened. 전부 sounds more mature and objective 그는 복권당첨된 돈을 전부 탕진하였다 He wasted all the money he won at the lottery. 학급 전체가 행사에 참석하였다. Everyone of the class participated at the ceremony. 새로운 규정들은 전체 임직원들에게 즉각적으로 반영된다. The new regulations apply to the whole staff with immedate effect. 몇몇 곡은 좋지만 이 앨범은 전체적으로 균형이 맞지 않는다. Even though some tracks are nice, the balance isn't quite right in this album as a whole. ============================================================= 다: uncountable 전부: countable 동생이 병의 물을 다 쏟아버렸다: 전부 would be incorrect since water isn't countable 동생이 내 과자를 다 먹어버렸다: Your younger sibling might or might not have eaten all of your cookies. You might be exaggerating, feeling robbed since your younger sibling ate quite a lot (without your permission). 동생이 내 과자를 전부 먹어버렸다: He actually ate all of your cookies. It's a blunt fact. 전체 is something very different as you can see in the examples above.

The essential difference among the three is their etymology. 다 is a pure Korean word meaning it is a phonetic signifier that people agreed its meaning. 전부 & 전체 has Chinese origin. 다: all (generic) 전부: all parts 전체: whole body (body here is metaphorical), entirety, totality. So very strictly speaking they all differ in their nuances. But in practice, people mix'em.