"실질적 and 현실적"
They share the sense of "practical" or "practically useful" but there is a difference.
- 실질적: 실(real), 질(base, quality), 적(like, -ish)
Of true, actual value as opposed to more abstract one like reputation or appearance.
Ex: 이 정책의 실질적 효과는 미미하다: Actual effects of this policy is meager.
- 현실적: 현(present, manifest), 실(real). 현실 = reality
Suited to, useful for life at hand as opposed to general goodness.
Ex: 그는 현실적 계산이 빠르다: He shrewdly figures out what's best for himself.
* Apart from "usefulness" 현실적 has another meaning: "(actually occurring) in real life".
The dictionary lists this sense first, so it is probably more widely used in this sense.
- 현실적 여건 (real circumstances, actual conditions)
- 비현실적 (unrealistic)
- 현실적 고통 (day-to-day hardship)