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'.
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ETYMOLOGY

KOREAN 3.0 Eng Wordtype Etym. Gb Vie
☆ DIFFICULT; TOUGH; PAINSTAKING; STRENUOUS Adjective 吃力，费劲，艰难 vất vả, gian khổ, khó khăn, gian nan