The world of One Piece is populated by humans and numerous other races, including mermen and mermaids, "fishmen" (a race of fish/human hybrids), and giants. It is covered by two vast oceans, which are divided by a massive mountain range called the Red Line (赤い土の大陸（レッドライン） Reddo Rain?).[6] The Grand Line (偉大なる航路（グランドライン） Gurando Rain), a sea that runs perpendicular to the Red Line, further divides them into four seas: North Blue (北の海（ノースブルー） Nōsu Burū), East Blue (東の海（イーストブルー） Īsuto Burū), West Blue (西の海（ウェストブルー） Uesuto Burū) and South Blue (南の海（サウスブルー） Sausu Burū).[7] Surrounding the Grand Line are two regions called Calm Belts (凪の帯（カームベルト） kāmu beruto), which experience almost no wind and ocean currents and are breeding ground for the huge sea creatures called neptunians (海王類 kaiōrui, lit. "sea kings"). Because of this, the calm belts are very effective barriers for those trying to enter the Grand Line.[8] While marine ships, using sea-prism stone (海楼石 kairōseki) to mask their presence, can simply pass through,[9] most have to use the canal system of Reverse Mountain (リヴァース・マウンテン Rivāsu Maunten), a mountain at the first intersection of the Grand Line and the Red Line. Sea water from each of the four seas runs up that mountain and merges at the top to flow down a fifth canal and into the first half of the Grand Line.[10] The second half of the Grand Line, beyond the second intersection with the Red Line, is also known as the New World (新世界 Shin Sekai).[11]
The currents and weather on the Grand Line's open sea are extremely unpredictable, whereas in the vicinity of islands the climate is stable.[12] What makes it even harder to navigate is the fact that normal compasses do not work there.[13] A special compass called a Log Pose (記録指針（ログポース） Rogu Pōsu?) must be used.[14] The Log Pose works by locking on to one island's magnetic field and then locking on to another island's magnetic field.[15] The time for it to set depends on the island.[16] This process can be bypassed by obtaining an Eternal Pose (永久指針（エターナルポース） Etānaru Pōsu), a Log Pose variation that is permanently set to a specific island and never changes.[17]
The world of One Piece is filled with anachronisms, like the Transponder Snails (電伝虫 Den-Den Mushi?), snail-like animals that can be attached to electric equipment and function as rotary phones,[18] fax machines,[18] surveillance cameras,[19] and similar devices.[19] Dials (貝（ダイアル） daiaru), the shells of certain sky-dwelling animals, can be used to store kinetic energy, wind, sound, images, heat, and the like and have various applications.[20]
A Devil Fruit (悪魔の実 Akuma no Mi) is a type of fruit which when eaten confers a power on the eater.[21] There are three categories of Devil Fruit.[22] Zoan (動物系（ゾオン） Zoon) fruits allow the user to fully and partially transform into a specific animal (real or otherwise [some fruits allow a person to turn into mythical beast such as a phoenix or a dragon.])..[23] Logia (自然系（ロギア） Rogia) fruits give control over and allow the user "to change their living body structure into the powers of nature".[22] Paramecia (超人系（パラミシア） Paramishia) is a catch-all category for fruits that give the user superhuman abilities.[24] They are said to be incarnations of the Sea Devil himself, and as a result, Devil Fruit users cannot swim in sea water, as "they are hated by the sea".[25] When even partially submerged in sea water, they lose all of their strength and coordination, although some abilities remain, such as Luffy still being able to stretch after being totally submerged. "Moving" water, such as rain or waves, does not have this effect. When a Devil Fruit user dies, the powers will be reincarnated into a new Devil Fruit.[26]
Haki (覇気?, lit. "Ambition") is a latent ability every living being in the world of One Piece possesses, though it is quiescent in most. It comes in three varieties: Color of Observation Haki (見聞色の覇気 Kenbunshoku no Haki) allows to sense the presence of other beings and predict their movement. Color of Armament (武装色の覇気 Busōshoku no Haki) allows one to envelop body parts and even inanimate forms with a force akin to an invisible armor that possesses defensive/offensive properties, which also allows one to inflict harm upon Devil Fruit users. The rare Color of the Conquering King (覇王色の覇気 Haōshoku no Haki) enables one to intimidate or render beings of weak determination unconscious.
Production[edit]

While working as an assistant to Nobuhiro Watsuki, Eiichiro Oda began writing One Piece in 1996.[27] From there, it started as three one-shot stories entitled Romance Dawn[27]—which would later be used as the title for One Piece's first chapter and volume. The two one-shots featured the character of Luffy, and included elements that would later appear in the main series. The first of these short stories was published in August 1996 in a special issue of Weekly Shōnen Jump and later in One Piece Red. The second was published in the 41st issue of Weekly Shōnen Jump in 1996 and reprinted 1998 in Oda's short story collection, Wanted!.[28]
Oda originally planned One Piece to last five years, and he had already planned out the ending, but he found himself enjoying the story too much to end it in that amount of time and now has no idea how long it will take to reach that point.[29] Nevertheless, the author states, as of July 2007, that the ending will still be the one he had decided on from the beginning and he is committed to seeing it through to the end, no matter how many years it takes.[30]
When creating a Devil Fruit, Oda thinks of something that would fulfill a human desire; he added that he does not see why he would draw a Devil Fruit unless the fruit's appearance would entice one to eat it.[31] The names of many special attacks and other concepts in the manga consist of a form of punning, in which phrases written in kanji are paired with an idiosyncratic reading. The names of Luffy, Sanji, Chopper, Robin, and Franky's techniques are often mixed with other languages, and the names of a number of Zoro's sword techniques are designed as jokes; for example, some of them look fearsome when read by sight but sound like kinds of food when read aloud (like Zoro's signature move, Onigiri, which is rendered as demon's cut but may also mean rice dumpling). Eisaku Inoue, the animation director, has said that the creators did not use these kanji readings in the anime since they "might have cut down the laughs by about half."[32] Nevertheless, Konosuke Uda, the director, said that he believes that the creators "made the anime pretty close to the manga."[32]
Oda was "sensitive" about how his work would be translated.[33] The English version of the One Piece manga in many instances uses one onomatopoeia for multiple onomatopoeia used in the Japanese version. For instance, "saaa" (the sound of light rain, close to a mist) and "zaaa" (the sound of pouring rain) are both translated as "fshhhhhhh."[34] Unlike other manga artists, Oda draws everything that moves—including crowds, animals, smoke, clouds, and oceans—himself to create a consistent look while leaving his staff to draw the backgrounds based on sketches drawn by Oda.[35]
When a reader asked Oda who Nami is in love with, Oda answered that there will not likely be any romance among the Straw Hat Pirates. Oda explained that he does not portray romance in One Piece as the series is a shōnen manga, and the young boys who read the manga are not interested in romance.[36]