Glossary

The words the tools use, in plain English. Every term has its own link, like /glossary#buy-limit.

Everywhere on the site

Flip: Buying an item for less than other players pay for it, and selling it again. The profit is in the gap between the two prices.
Margin: What you keep from one item: the price you sell for, minus the price you paid, minus the game's tax or fees.
ROI: Return on investment: the margin as a share of what you paid. 5% ROI means 5 gold back on every 100 you put in.
Volume: How many of an item traded in a period, usually the last 24 hours. Low volume means your offers can take long to fill.
Gold per hour: What an activity earns in an hour of play at today's prices. It depends on how fast you are, so the tools ask for your own rate.
Price age: How long ago a price was last seen in a real trade. An old price may not be there any more when you try it.

Old School RuneScape

Grand Exchange (GE): The game's trading post, in Varrock. You put in an offer to buy or sell at a price, and it fills when another player's offer matches.
Buy price (instant sell): The last price someone got when they sold an item right away. Put in a buy offer at about this price and wait for a seller.
Sell price (instant buy): The last price someone paid to buy an item right away. Put in a sell offer at about this price and wait for a buyer.
GE tax: 2% of the sale price of each item, rounded down, and at most 5,000,000 gp per item. Items that sell for under 50 gp pay none, and a few items, like bonds, are exempt.
Buy limit: The most of one item you may buy on the Grand Exchange in 4 hours. It caps what a flip can earn: margin × buy limit per 4 hours.
Limit profit: Margin × buy limit: the most one buy limit can earn you, if the market sells you that many in time.
Held: In how many of the last 24 hours a margin was there, going by each hour's average prices after tax. A margin that held 20 of 24 hours is one you can count on.
Unusual price: A price far from the item's 6-hour average, usually from one odd trade. The margin it shows is rarely there for you.
Members and free-to-play (F2P): Members items can only be used, and bought or sold, on a paid membership. F2P players can trade the rest.
Noted: Items as a stackable note instead of one per inventory slot. Many drops come noted, and so can what you collect from the Grand Exchange.
High alchemy (alching): A spell that turns an item into its high-alch value in coins. It costs a nature rune a cast, plus fire runes a fire staff can supply.
Unfinished potion (unf): A clean herb in a vial of water, the first step of most potions.
Decanting: Bob Barter at the Grand Exchange changes potions between dose sizes, which sometimes sell for different prices per dose.
Hiscores: The official list of every player's levels, boss kill counts, raids and clue scrolls. Enter your name on the OSRS page and the tools show what your levels allow, and your kills and clues next to what they are worth.
Ironman: An account type that can't trade with others, so market tools are of little use to it.
Purple (raid unique): A rare reward from a raid, named after the purple light it drops with. Most of a raid's value is in these.
Reward casket: The box at the end of a clue scroll trail. It rolls its reward table a few times (one to three for a beginner casket, five to seven for a master), and each roll gives one reward.
Mega-rare table: The rarest branch of a casket's rewards, where gilded and 3rd age items sit. A roll lands there once in thousands of rolls; the 3rd age items carry much of a casket's average value.
The Mimic: An elite or master casket that turns out to be a monster (1 in 35 and 1 in 15, once you have enabled it at Watson's strange casket). Beating it gives extra loot on top of the casket's rolls.
Task weight: How often a Slayer master hands out a task, relative to the rest of the list. A task's chance is its weight divided by the total of all the master's weights.
Block and skip: A Slayer task you skip is replaced for 30 points; a blocked task is never assigned again by that master (6 to 7 block slots). For money, block the common tasks that earn least.
Bond (Old school bond): The item Jagex sells for real money that players trade on the Grand Exchange and redeem for 14 days of membership. It pays no GE tax; its price is what membership costs in gold.
Buy limit window: The 4 hours in which an item's buy limit counts. It starts at your first purchase of the item and ends 4 hours later, whatever you bought after; then the whole limit is free again.
Bank value: What everything in your bank would bring: on the Grand Exchange at the last instant-sell prices after tax, or at Jagex's daily guide prices. Items that cannot be sold count for nothing.
Harvest lives: How many picks a herb, seaweed or similar patch has left: 3, plus 1 for each tier of compost. Each pick has a chance not to use one up, higher at a higher Farming level, so the average harvest is well above the lives.
Protection payment: Produce you give the gardener next to a patch, like 25 coconuts for a magic tree, so the plant can't die of disease. Tree runs usually pay it, since a dead tree gives no XP.
Bird nest: Found while chopping trees and in bird houses: a seed nest holds a tree or fruit tree seed, a ring nest a ring. Searching one leaves an empty nest, which sells for Saradomin brews.
Kingdom approval: How much the people of Miscellania like you, from 25% to 100%. Your kingdom gathers more the higher it is; it drops a little each day unless you work on the islands.

Albion Online

Tier and enchantment (6.4): An item's tier runs from 1 to 8 and its enchantment from 0 to 4. Players write both as one number: 6.4 is tier 6, enchantment 4.
Quality: Normal, Good, Outstanding, Excellent or Masterpiece. Crafting rolls it; better quality sells for more.
Sell order and buy order: A sell order lists your item at your price until someone buys it; a buy order waits for someone to sell to you. Selling straight into a buy order is instant.
Market tax and setup fee: Selling costs 4% tax with Albion premium, 8% without. Listing a sell or buy order costs a further 2.5% setup fee.
Black Market: A market in Caerleon that buys gear to stock the loot of monsters. It often pays more than the cities, but only buys.
Red zone: Areas where other players can attack you and take everything you carry. The route to Caerleon and the Black Market crosses them.
Return rate: The share of the materials you get back when you craft or refine: more in a city with a bonus for that item, and more with focus.
Focus: Points you gain each day and spend on crafting or refining for a much higher return rate. The Focus tool shows where they earn most.
Bonus city: Each royal city has a bonus for a few crafting categories and for one refined resource, which raises the return rate there.
Station fee: What the owner of a crafting or refining station charges to use it, set per 100 nutrition the item needs.
Item power (IP): The strength of a piece of gear: 700 at tier 4 and 100 more per tier or enchantment level, plus a bonus for quality (up to 100 for a masterpiece). A build needs a certain item power, which several tiers and enchantments can give.
City flip: Buying and selling in the same city: a buy order just above the best one, then a sell order just under the cheapest. Both orders pay the setup fee, the sale pays the tax.
Upgrade flip: Enchanting an item with runes, souls or relics before selling it to the Black Market, when the enchanted one fetches more than the plain one plus the materials.
Seed and offspring yield: The chance a harvested crop gives its seed back, or a grown animal leaves a baby. Watering a crop or nurturing an animal with focus raises it, sometimes past 100%.
Local yield bonus: Islands at each city grow a few crops, herbs or animal products 10% better; farms in Outlands hideouts grow every crop and herb far better.
Journal: A laborer's work order. Your own gathering, crafting, fishing or fighting fills it with fame; a full one sends the laborer on a 22-hour job and comes back empty with the resources.
Laborer happiness: How a laborer feels about their bed, table and trophies, on a bar of 9 segments. The happier, the more they bring back: from 100% of the journal's base amount up to 150%.
Gold: The currency Albion sells for real money. Players trade it for silver on the in-game gold market, so it has a silver price that moves, and premium, bought with gold, has a price in silver.
Fame: What the game awards for fighting, gathering, crafting, fishing and farming; it fills your destiny board. Your lifetime fame per activity is on your public profile, which you can link on the Albion page.

MapleStory Classic

Mesos: The game's money.
Free Market: The area where players open shops and sell to each other. Its prices are what players report on GameMargins.
Scroll: Adds stats to a piece of equipment, with a chance to fail. Each try uses one of the item's upgrade slots.
Upgrade slots: How many scrolls an item can still take. A clean item has all its slots unused.
NPC shop: A shop run by the game. Some sell below what players pay in the Free Market, and some buy above it.

WoW: Forever

Auction house (AH): Where players sell to each other. It keeps 5% of each sale.
Vendor: A game shopkeeper. Vendors sell some reagents cheaper than the auction house, and buy anything at a fixed price.
Reagent: A material a recipe uses.
Skill colours: A recipe is orange, yellow, green or grey for your skill: orange always raises it, yellow usually, green now and then, grey never.
Market (region, ruleset and faction): Each region, ruleset (normal, PvP or RP) and faction has its own auction house and prices; pick yours at the top of a page.