공정하다: 공(公): fair, equitable to all; 정(正): just, right => fair and just 정당하다: 정(正): just, right; 당(當): proper, reasonable => just and legitimate 달리다 and 뛰다 are nearly the same when they mean "run". They have different usage when applied more widely. 달리는 기차(O), 뛰는 기차(X) -> 달리다 can be applied to vehicles, 뛰다 can't. 뛰는 물가(O), 달리는 물가(X) -> 뛰다 means "jump" as well, 달리다 does not.