1 (wiktionary) 2 (vi.wikipedia) 3 (en.wikipedia) 4 (glosbe)

Core Words Familarize yourself with the 'core words'.
Compounds Expand your vocabulary by studying more complex words built by the 'core words'.
Wordsense Learn about the wordsenses of the english term.

ETYMOLOGY

HAN VIET: vô hiệu 无効

KOREAN 3.0	Eng	Wordtype	Etym.	Gb	Vie
☆	INVALIDITY	Noun	无效	无效，作废	vô hiệu