A vendor is an NPC who buys and sells items. Trainers are not technically vendors, even though they sell recipes, since they do not buy anything. The word is also sometimes used as a verb for selling to a vendor, e.g., "I'm just going to vendor this axe, since I can't use it." For quick use as a verb, sometimes only "V" is used to mean "vendor it" or "V?" for "vendor it?" Items that have no use other than selling to a vendor are called vendor trash.
It is noteworthy that while most profession and food vendors are essential, most armor and weapon merchants are only as valuable as their repairs. The items they sell are expensive, have no stats, and are almost always completely inferior to items of the same level. They have little to no use after around level 10, when drops and quest rewards become better.
As of Patch 2.3, your pointer changes when you move it over a repair-capable NPC:
If you sold an item, you can buy it back for the same price at which it was sold by clicking the Buyback tab and right-clicking the item or dragging it back to your bag. You can repurchase up to 12 items that you have sold to a vendor. The items (up to 12) since you last logged in will persist. When your character leaves the game or zones to a different area, this list of items will be cleared, so if you have accidentally sold something, don't wait to buy it back. To this date, no raid is yet Vendor proof. Buy it back immediately.
This section concerns content exclusive to Mists of Pandaria.
The Beta introduced type filters on vendors which should make it easier to find items. The drop-down will appear on the upper right of the vendor window and will filter based on the viewer's class specs or whether the item is bind on equip.
Armor and weapons
A few items may be used as portable vendors; players can bring them with them as items or abilities to access a vendor anywhere in the game. This is very useful as it saves a lot of time to not have to return to a stationary vendor every time you have to sell and in some cases buy something. Examples of portable vendors are:
- (requires Engineering 450 to use, can repair)
- (requires Engineering 425 to use, can repair)
- (requires Engineering 325 to use, can repair)
- (requires Engineering 300 to use, can repair)
- / (when upgraded with a )
- (has repair vendor)
- (requires guild achievement Profit Sharing and revered reputation with guild to purchase)
- (requires guild achievement Horde Slayer/Alliance Slayer and honored reputation with guild to purchase)
Notice that portable vendors, while most sought for as convenient buyers of useless things that players don't need, often offer a somewhat meager choice of items that players may buy for self-usage. The average portable vendor is much similar to a reagent-vendor, selling common items which players need in order to cast their spells. Portable vendors also often sell poisons used by Rogues, materials used in various professions, sometimes food and in rare cases equipment. Some portable vendors can also repair, thus they are often popular in raids or instances.