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'.
Etymology Explore the origin of the 'core words'.

{n}	substitute	(a player who is available to replace another if the need arises)	Ersatzspieler {m}
{n}	substitute	(a replacement or stand-in)	Ersatz {m}
{v}	substitute	(to use in place of something else, with the same function)	ersetzen