With TFT being out for a couple of years, there are some terms that all players should know to properly understand all the aspects of the game. While this guide is comprehensive, it does not include all terms used in the game, but rather the most popular ones which you'll always encounter in your day-to-day games. Here are the most common terms in TFT:
Ability - a passive or active ability that is either permanently available or cast when the unit reaches full mana.
Ability power (AP) - the main stat for mage units, empowering their abilities depending on the scaling.
Arena - the battlefield of TFT, which includes the board for units to fight, the unit bench, and the Gold Generators.
Bench (unit or item) - the area below a player's board that can hold units or the area to the left of a player's board that can hold items.
Board - the center area of the arena where units fight each other.
Buff - can either refer to a positive change that a unit receives during a patch or to the bonuses received from stacking a certain trait.
Bug - programming error in the game that results in an unintended consequence.
Build - can either refer to certain items to use on a unit or a specific combination of units.
Carousel - the round where players pick a combination of a unit with an item from a shared pool.
Carry - a strong unit in which you invest resources for them to carry the game.
Comp (composition) - a specific combination of units and items. Can be used interchangeably with build.
Counter - a build that can counter another build due to specific traits that make them take less damage, do increased damage, or avoid powerful effects due to their specific traits.
Economy - the general concept of building up your gold in the game, which is the main currency to acquire units, level up, or reroll the available units to buy.
Experience (XP) - the mechanic which determines your level. The higher the level, the more experience required to level up.
Ghost - playing against a copy of an enemy's board when there is an odd number of players left in the game. If you win the round, no damage will be done to the opposing player whose board has been copied. If you lose the round, you will take damage as during a normal round.
Hextech augments - a mechanic introduced in set 6, giving players 3 options to choose from during the game, which can completely change your playstyle.
Hypercarry - a high-cost unit that usually takes over the game if properly invested into.
High roll - usually signifies that the player was lucky in their rolls, getting the required item components or units.
Little legend - the avatar used by the player during the game.
Low roll - usually signifies that the player was unlucky in their rolls, getting the opposite of what they wanted for their build.
League points (LP) - the points awarded or taken from a player after the results of a ranked game.
Mana - the secondary resource used to cast abilities.
Mana-lock - the time it takes a unit to start generating mana after casting a spell.
Matchmaking - the system behind matching the players for a game.
Meta - the current strong compositions which dominate the game and are proven to be the most effective.
Nerf - a negative change a unit receives during a patch.
Overpowered (OP) - used to describe a unit or tactic that is much stronger than the rest.
Overtime - the extra time once the round timer runs out in which units gain increased attack speed, ability power, and less healing alongside less crowd control duration.
Public beta environment (PBE) - testing server where Riot ships changes to see how they impact the game before shipping them to the live server.
Positioning - relates to how players put their units on the board.
Pivot/transition - changing your current build to a new one. The reason behind it could be that there are too many players going for the same build or that you received some units or items that will benefit you more if you changed your build.
Player vs. Player (PvP) - rounds when players fight each other.
Player vs. Environment (PvE) - rounds when a player fights a neutral enemy.
Scouting - looking at the enemies' board to understand what they are building to understand how to use that to your advantage.
Set - period of time with its specific units, items, traits, and mechanics.
Splashable - a unit that can easily fit into multiple builds due to their utility.
Stage - a group of rounds. The first stage has 3 rounds while all other stages have 6 rounds.
Streaking - bonus gold gained due to a win or lose streak.
Trait - class or origin of a unit. If you have multiple units of the same trait, you will gain various bonuses depending on the threshold to gain those bonuses for each trait.