AppearanceNami is a young attractive woman with short, orange hair and a relatively slim build. She has a tattoo on her left shoulder which represents mikan and pinwheels (a homage to Bellemere and Genzo, respectively), where she used to have a tattoo for being a member of Arlong's Crew. Near the beginning of the series, Nami wore thick, low cut leather boots and a simple blouse. However, during the Arlong Park arc and thereafter, Nami wore open-toed shoes and more revealing outfits (With the tattoo no longer being a secret). She seemed to have abandoned the shoes for high-heeled boots as of Chapter 435. She usually pairs her tops with skirts with rings on them. Her overall physique matured suddenly (though this is, most likely, a simple change in style of artwork). Her fashion frequently changes as well as her hair style. Many of her shirts feature four-letter words, such as "MODE," "GOLD" or "EVIL," similar to a shirt that Bellemere once wore that had "MACE" on it.
In SBS Volume 6, Oda said, according to Sanji, her measurements were 86-57-86cm = 34-22-34". The author has also replied to a fan's question saying that right now Nami's measurements are as follows:
Height: 169cm = 5' 6½"
Measurements (B-W-H): 95-55-85cm = 37-21-33"
He later also specified that Nami has D-cup size breasts. However, her breasts seem to grow into and then "reset" throughout the arcs (this is much more obvious in the manga and in one of the movies). He has also said that Nami resembles a cat, that he uses the color orange to represent her, and she smells of mikan and money.
PersonalityAlong with Nico Robin, Nami is one of the smartest of the Straw Hats and the third smartest character in East Blue according to Oda, the first being Ben Beckman of the Red-Haired pirates and the 2nd being Captain Kuro . At the beginning of the series, Nami despised all pirates. She viewed them as nothing but bad people after losing someone close to her, only changing her mind after she met Luffy and Zoro. Before her view changed on pirates, she was perfectly fine with giving Luffy up captive to Buggy, as she could not bring herself to stoop to their level.
Nami's money eyes
Nami is greedy and will do anything for money, accepting any challenge that comes along. Her love of money stems from her childhood, where she lived a poor life and was often upset at having little wealth despite the love of her adopted mother. While she will send in Luffy, Zoro and the rest of the crew to meet the demand, the one thing she will not do is sell out a friend; no matter what the sum. She takes control of the amount of money the crew spends, ever aware of the crews spending habits (such as Luffy's desire to spend all they have on meat) and tries her hardest to avoid it getting spent all at once. To this end, she is in complete horror whenever the rest of the crew wastes money or passes up an opportunity to get it. She is loyal to her money, but no matter how much she denies it, she is loyal to her friends first.
Nami is very bossy and is usually ordering everyone around, including Luffy, despite not even being the captain herself. Nami's main concern when she is in trouble is herself first and usually has other members do her fighting, resulting in her fighting in fewer fights. She is a coward, though not on the same level as Usopp, her cowardice has more to do with survival. She is aware of dangers they face every day and has a much better understanding of the world and its more dangerous individuals(ex. the Shichibukai) than most of her crew, though lacks Robin's knowledge on some of its other powerful figures (ex. the marine Admirals). She can be devilish at times and won't think twice about ditching the others to save her own life.  She has been known to stand her ground against anyone hurting her friends, abandoning her otherwise normal routine of trying to stay out of harm's way. 
Nami also has an obsession with fashion, as she is never seen wearing the same clothes. This was not present in the early chapters and started after the Captain Kuro arc.  When Nami goes shopping, she sometimes goes to exquisite boutiques and tries on stuff, just to leave stating that she is searching for something more casual. She doesn't seem to have much modesty as she sometimes wears rather skimpy clothing and allows people to take photos of her in a swimsuit (as long as they pay). She even doesn't have any problems with men seeing her naked as she showed her body to the crew so they would stop watching Vivi and her. Also, she changed her clothes in full view on a sea train. However, if someone does see her naked, she charges image:bsymbol.gif100,000 per view. She also doesn't like people insulting her navigating skills.
CrewNami at first was excited to join the crew but grew more reluctant when she learned that Luffy is a pirate because of her disgust at pirates. She betrayed Luffy and even wished him dead before he formed a crew. Her original membership into the crew was just as an "alliance" with Luffy which she later ended to return to her home village, however by then she had become fond of the crew and found it was not so easy to just leave. . After Arlong's defeat she officially joined the crew, by then she had completely changed her mind on her fellow crewmates.
She soon came to respect Luffy's qualities as a leader, but often gets angry at his irrational thinking and short attention span. In such situations, she sometimes tends to get into violent outbreaks. Her sudden violent outbreaks may also be caused by traits of other crew members such as Roronoa Zoro's sleeping. Despite this, she trusts Luffy very much as her captain.
She also often takes advantage of Sanji with his devotion to her, ordering him to do her bidding. She also uses Usopp to maintain her weapons (and wriggling out of paying him for his service). Zoro tries not to fall for her manipulative schemes, but ends up a victim like the rest, usually due to debt, after Nami tricks him into accepting a image:bsymbol.gif100,000 loan and forces him to pay it back three times over despite him not spending it and giving it back. The two also tend to get into arguments due to their somewhat similar personalities. She is still shown to care for him, as she does the rest of the crew. Nami occasionally gets irritated with Franky (such as when he calls her "girlie"), but still trusts him.
Nami gets along best with Robin, who is the only one she does not attempt to boss around. She often refers to her as "onee-sama" or "Robin-nee-san," both commonly used for elder sisters, and often spends time with her. When Nami goes shopping, she is often accompanied by a smiling Robin.
FriendsBack home, Genzo acted as a father figure to both Nami and Nojiko. He was shown very concerned about Nami's pose on her bounty attracting more perverts than bounty hunters, although he had an enlarged picture of it himself. Amusing considering the fact that he is more concerned about her picture than Nami being arrested. The rest of the village still adores her.
Nami also shared a close relationship with Vivi, to the point of an almost sisterly bond. Like the rest of the crew, she was deeply upset about her leaving.
She also made a good friend of Lola the zombie warthog, to the point where she even help set Lola and Absalom up for marriage. Their friendship transcended over into the real Lola when Thriller Bark was taken down. Lola had a strange feeling she already knew Nami from somewhere else despite never meeting her before, Nami was just happy to see her friend. To date, Lola has been the only person Nami has willingly handed some of her treasure over to.  Lola now regards Nami as a sister, to ensure her and her friends were safe she gave Nami half of her Biblicard for her mother.
EnemiesNami is an enemy to the Marines, as she carries a bounty on her head. Arlong and his pirates were her enemies for a long time; despite Arlong taking her into his crew she showed no love for them due to what they did to her village and for killing Bellemere. Arlong had fought Luffy claiming that she was his crewmate in his fight, even admitting she was 'cute' for a human and admitted he had no respect for humans yet she was one of about 2 humans he was seen to show respect for, the other being Nezumi. She has stated that she has not forgiven Hatchan for what he did as part of the Arlong Pirates, but after seeing him get shot trying to hold Luffy back and hearing him say that he had hoped to do what he could to make up for what he had done, becomes concerned about his well-being.
BellemereShe has comes to terms with the idea Bellemere was her mother. In life she never saw eye to eye with her adoptive mother at times, in death Nami deeply missed her due to the fact she knew Bellemere deeply loved her despite everything. Nami is seen drawing a picture of her after being forced into Arlong's crew, and sadly calling out her name in a moment of misery. She regularly visited her grave on the cliff top where she was buried and often thought about her.
NojikoNami values Nojiko as the only person who loved and supported her through her years of stealing to buy the village. Though not related by blood, she supports Nami like a real sister. When Nami received her tattoo for being on Arlong's crew, Nojiko responded by getting her own tattoo to match Nami. When Nami removed Arlong's tattoo, she replaced it with her current one so she still matched her sister.
OtherAs an orphan, Nami may have other family. However considering the circumstances behind her origins with Bellemere and Nojiko and the fact Bellemere found both girls in a war zone, it seems unlikely this will ever be touched upon.
Abilities and PowersNami is a highly skilled navigator as well as a talented cartographer. She is capable of formulating advanced equations in mere minutes to predict a precise course of action, although she usually needs to write the equations down on a physical medium when formulating them. She has the innate ability to sense changes in the weather, and can even predict the appearance of supposedly unpredictable cyclones in the Grand Line despite running a high fever. This attribute proved useful during Nami's one-on-one "fight" with Eneru, where she managed to deflect several of the Goro Goro No Mi user's lightning-based attacks using only Thunder Balls from her Clima-Tact. She's also an excellent thief and pickpocket. Small items, keys, without the victim noticing (she is shown stealing even as a little girl). It was shown before she left her village at the harbor, stealing almost all wallets from the people saying goodbye to her while running without anyone noticing before she reveals it.
Throughout most of the series up to the Water 7 arc, Nami was not as skilled in combat as most of her crew; she is not especially strong, nor does she have formal training in any fighting style, although she was shown in the Water 7 arc to have decent agility, being able to jump over a gate and between rooftops. As a result, she remained a supporting member of the crew rather than a main fighter. Before acquiring the Clima-Tact and its upgrades, she possessed moderate skill with a Bo staff she used for self-defense. However, she was often outmatched by the monstrous foes they met at sea, and typically manipulated one of her crewmates to fight in her place or fled when the situation turned dangerous. With the Clima-Tact, this habit slowly began to disappear.
WeaponsNami relied on a standard wooden staff throughout the East Blue saga and kept it until the Arabasta arc. During that arc, Usopp invented her a weapon called the "Clima-Tact." Although the Clima-Tact initially seemed like a useless tool, Nami managed to unlock its potential and fight a major battle in a nonsupporting role, earning her first victory by defeating Miss Doublefinger. However, despite her improved fighting potential, she still stuck to the old tactics she employed before the Arabasta arc, sending in her crewmates when she sensed danger and/or running away.
Some time before or during the the Water 7 arc, Usopp improved the Clima-Tact with Dials, creating the "Perfect Clima-Tact". This new weapon was powerful enough to wipe out an entire group of Marines, and was effective enough to help Nami defeat CP9's Kalifa. Following the Straw Hat's battle with CP9 at Enies Lobby, Nami has been engaging in combat more actively, and is shown confidently brandishing her Perfect Clima-Tact at any sign of confrontation. By earning a bounty, Nami has proven herself to be more than a navigator, and with her Perfect Clima-Tact, she has grown to become a legitimate fighting pirate in the Straw Hat crew.
Other TechniquesThough infrequent, Nami has a couple of other moves that she can use to incapacitate (in more ways than one) her opponents.
* Shiawase Punch (幸せパンチ(しあわせ), Happiness Punch): A "technique" that Nami uses to dispatch Peeping Toms while she bathes; she simply drops her towel, causing any male in the vicinity to collapse from a massive nosebleed. She also uses this as a get-rich-quick scheme, as she charges image:bsymbol.gif100,000 to anyone who sees her doing this.
* Impact (衝撃貝 (インパクト)): Nami uses an Impact Dial to absorb attacks and then send them back at her opponents. This was shown only when she finished off Hotori with Gan Fall. Sadly though, she is not yet strong enough to do this technique without causing serious damage to her arm and great pain, which is perhaps why she hasn't used it more often.