Tie, result

단결(하다) = unity
연결(하다) = link, connection (연 = connect)
결합(하다) = union
결혼(하다) = marriage
결과 = result
결국 = eventually, conclusion (국 = position, circumstances)
결론 = conclusion (론 = discuss)

Absence, defect

출결 = attendance and absence
결석(하다) = absence (school)
결근(하다) = absence (work)
결시(하다) = absence (exam, test)
결함 = defect, fault (product)
결점 = weak point, defect, fault (person)
결핍 = shortage, deficiency
결례 = lack of courtesy, negligence in etiquette
결격 = disqualification
결번 = not valid(in service) number

Decide

결정(하다) = decision
결심(하다) = resolution
결코 = absolutely not, never

Clean, pure

순결(하다) = purity
결백(하다) = innocence, purity
결벽증 = excessive love of cleanliness