悪魔の実
Devil Fruit
Mysterious "treasures of the sea" that grant supernatural powers at the cost of ever swimming again; where they come from is one of the series' longest-guarded mysteries.
ゴムゴムの実
Gomu Gomu no Mi
The rubber Devil Fruit Luffy ate as a child — VIZ's "Gum-Gum Fruit," whose English name famously wobbled through fruit, Devil Fruit and an invented "Gum-Gum Tree" in the early volumes.
偉大なる航路
Grand Line
The sea route where the One Piece waits — "they call it the pirates' graveyard" (Coby, Vol. 1, p.81).
覇気
Haki
Latent will-energy introduced much later in the series, projected as armor, observation, or pure conqueror's intent.
一味
Ichimi
The crew as an institution — 麦わらの一味, "the Straw Hat Crew." The organizational counterpart to the personal bond of 仲間; VIZ's "crew" maps this word exactly.
仲間
Nakama
The series' thesis word: someone inside your circle, bound by shared stakes rather than mere affection. A membership word, not a friendship word — and famously resistant to English, with five different official renderings in the first crew arcs.
ひとつなぎの大秘宝
One Piece
Gold Roger's treasure and the series' title: literally "the great secret treasure of one-connection" (ひとつなぎ), a unity pun the English name can't show. First spoken aloud by Coby in Vol. 1, p.72.