This is the 3825th most frequent Korean word.
실질적
Practical or substantial.
In this sentence, "실질적인" is used to describe a type of evidence ("증거") as being substantial or concrete, emphasizing its importance and authenticity.
실질적인 증거가 없는 주장에 신뢰를 두기 어렵습니다.
It is difficult to trust a claim without concrete evidence.
Here, "실질적인" modifies "변화" (change), indicating that the change was real and significant, not superficial.
그 프로젝트는 실질적인 변화를 가져왔습니다.
That project brought about substantial change.
In this example, "실질적인" is used with "어려움" (difficulties) to denote tangible or real challenges that students face.