Skills

«Skills» are features/abilities a player can use in a game. These can be trained and leveled up to gain perks or abilities for the skill. There are various types of skills in the game including: Sword Skills, General Skills, Unique Skills, Outside System Skills, Original Sword Skills and Extra Skills.

Weapon Skills
Also see Sword Skills

There are several different classes of Weapon Skills. There are generic weapon skills such as «One-handed Straight Sword» and «One-handed Curved Sword». Then, there are additional weapon skills that can be unlocked after fulfilling a certain set of conditions. For example, in the sword category, the «One-handed Straight Sword» skill must be trained quite a bit before «Rapier» and «Two-Handed Sword» appears on the weapon skills list.

Weapon skills that do not have clear conditions for appearing are called Extra Skills. There are roughly around ten known Extra Skills, including the «Katana Skill» wielded by Klein. Each of these extra skills have at least ten people in the Sword Art Online world who practice the skill.

There are only two known Unique Skills, which are weapon skills unique to a single player. These are Heathcliff's «Holy Sword» and Kirito's «Dual Blades».

List of General Skills in Sword Art Online
In general, skills must be equipped in a limited amount of skill slots. Kirito, at the end of SAO, had 12 skill slots. Skills may be trained up to level 1000, at which it is considered «Mastered». There is rumored to be an unlimited number of skills in Sword Art Online.

Non-Combat Skills

 * Fishing - The effectiveness with which a player can catch fish. Higher levels catch rarer fish more often.
 * Musical Instrument - The effectiveness with which a player uses an instrument. Some instruments can have status changing capabilities.
 * Sewing - The effectiveness with which a player can craft lightweight cloth, leather, and monster hide armour.
 * Cooking - The effectiveness with which a player can combine ingredients to create carieties of food, some of which can have medicinal properties.
 * Equipment Appraisal - The ability to identify the Maker, Style, Damage Level/Defense Level, Name, Enchantments and Durability of a piece of equipment. Higher levels give more information.
 * Tools Appraisal
 * Purchase Negotiation - The effectiveness with which a player can barter when purchasing from NPCs.
 * Sales Negotiation - The effectiveness with which a player can barter when selling items to NPCs.
 * Medicine Mixing - The effectiveness with which a player can craft potions and poison weapons.
 * Slash Weapon Forging - The effectiveness with which a player can craft Slashing Weapons.
 * Thrust Weapon Forging - The effectiveness with which a player can craft Stabbing Weapons.
 * Blunt Weapon Forging - The effectiveness with which a player can craft Blunt Weapons.
 * Light Metal Armor Forging - The effectiveness with which a player can craft Light Metal Armor.
 * Heavy Metal Armor Forging - The effectiveness with which a player can craft Heavy Metal Armor.
 * Metal Equipment Repairing - The effectiveness with which a player can repair equipment and tools.
 * Metal Refining - The effectiveness with which a player can turn raw ore into refined ingots of metal.
 * Familiar Recovery - A skill specifically for Beast Tamers. This skill allows the user the ability to heal a pet.
 * Familiar Communication - A skill specifically for Beast Tamers. This skill allows the user the ability to undersrand and communicate with friendly creatures.

Passive Skills

 * Searching
 * Tracking - Raises effectiveness while hunting monsters. Can be used to pursue a player whose name is known by displaying their footprints from a certain time. Greater mastery of the skill will allow the user to see the recent footprints of nearby «Hiding» players.
 * Listening - The ability to hear sounds from further away than normal. Maximum level grants the ability to hear through locked rooms.
 * Detection - A sixth sense, allowing the player to notice enemies and secrets from a distance. Greater mastery allows detection of monsters in «Hiding» status and primitive booby traps, such as snares and pitfalls.
 * Hiding - Allows for a person to disappear. Only works on targets that use visual tracking.
 * Acrobatics - Determines a player's jumping height and the ability to perform aerial maneuvers. Bottom level is the natural jumping height for the Player.
 * Night Vision - The player can see better in darker conditions.
 * X-Ray Vision - The ability to see through obstacles and walls. Max level can see through secure rooms. Does not work on clothes.
 * Sprint (Passive & Sword Skill) - This skill is both an activatable burst of speed, and a passive increase in the player's effectiveness at dodging strikes.
 * Extended Weight Limit - Increases inventory size and weight capacity.

Combat Skills

 * Parry - The ability to use an attack to block an opposing strike. Maximum level makes it possible to destroy an item currently at less than half of the maximum durability; anything with a durability above that will not be damaged.
 * Howl - Attracts the attention of NPC monsters and increases a player's Hate status effect. Often used by tanks to lure enemies to the player.
 * Battle Healing - Recover low amounts of HP over time during battle. It can be leveled up by constantly getting one's HP into the red zone.
 * Emergency Recovery
 * Meditation - «Extra Skill» Increases HP regeneration and decreases the remaining time of negative statuses by entering a mental concentration pose. Obtained in a 6th floor quest.
 * Light Metal Equipment - The effectiveness with which a player can use Light Metal Equipment.
 * Light Shield Equipment
 * Leather Equipment - The effectiveness with which a player can use Leather Equipment.
 * Heavy Metal Equipment - The effectiveness with which a player can use Heavy Metal Equipment.
 * Spiritual Light (hate skill)
 * Fighting Spirit (hate skill)

Weapon Skills

 * One-handed Straight Sword - The effectiveness with which a player can use longsword-like weapons (e.g. arming swords, estocs, gladius, spatha,  etc.).
 * One-handed Curved Blade - The effectiveness with which a player can use slashing-type weapons (e.g. broadswords, short swords, etc.).
 * One-handed Dagger - The effectiveness with which a player can use dagger-type weapons (ex. katars, knives, dirks, etc.).
 * One Handed Rapiers
 * One-handed Assault Spear
 * One-handed War Hammer
 * Two-handed Straight Sword
 * Two-handed Assault Spear
 * Two-handed Battle Axe
 * Blade Throwing - The effectiveness with which a player can use throwing weapons (e.g. Throwing Picks)
 * Martial Arts - «Extra Skill» Unlocked from a quest on the 2nd Floor.
 * Katana - «Extra Skill» Unlocked by frequent usage of One-handed Curved Blade.
 * Dual Blades - «Unique Skill» Given to the player with the fastest reaction time.
 * Holy Sword - «Unique Skill»
 * Darkness Blade - «Unique Skill»
 * Battoujutsu - «Unique Skill» Means "Sword Drawing."
 * Shurikenjutsu - «Unique Skill» Means "Concealed Weapons."
 * Infinite Spear - «Unique Skill»