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fullback vs. halfback

fullback

[fool-bak] / ˈfʊlˌbæk /

noun

Football.

a running back who lines up behind the quarterback and is farthest from the line of scrimmage.
the position played by this back.
(in soccer, Rugby, field hockey) a player stationed near the defended goal to carry out chiefly defensive duties.

halfback

[haf-bak, hahf-] / ˈhæfˌbæk, ˈhɑf- /

noun

Football.
1. one of two backs back who typically line up on each side of the fullback.
2. the position played by such a back.
(in soccer, Rugby, field hockey, etc.) a player stationed near the forward line to carry out chiefly offensive duties.