The following are brief definitions of terms related to Tetris and similar games.
The following is a legend detailing the functions of the various blocks used in the diagrams throughout the wiki articles.
|Empty playfield cell|
|Red block (commonly part of Z tetromino)|
|Orange block (commonly part of L tetromino)|
|Yellow block (commonly part of O tetromino)|
|Green block (commonly part of S tetromino)|
|Cyan block (commonly part of I tetromino)|
|Blue block (commonly part of J tetromino)|
|Purple block (commonly part of T tetromino)|
|Gray block (Garbage or Playfield wall)|
|Ghost piece or Line clear|
|Rotation center of a piece, a bomb in Bombliss, or any other specially marked block|
|Purple block for the T Tetromino when executing a T-Spin|
|Cell that has to be occupied for something (like a wallkick) to happen|
|Cell that cannot be occupied for something (like a wallkick) to happen|
- See G.
- Active piece
- Alternate term for falling piece.
- All Clear
- When the player clears the whole playfield without leaving any blocks behind. Also known as a Bravo.
- A term for entry delay originating from Japan.
- Arika Rotation System (ARS)
- The rotation system used by most games published by Arika.
- A class of randomizer in which a collection of pieces is shuffled, and all are dealt into the preview. (See Random Generator.)
- Base (T-Spin)
- The portion of a T-Spin setup, not directly under an overhang, where the T rests upon.
- A solid element occupying one cell of the playfield. Also used as a synonym for "cell" to represent a length or width (e.g. a 2-block-tall hole). Multiple blocks make a piece such as a tetromino. In some publications, a "block" may refer to a whole piece, but Tetriswiki uses "piece" or "tetromino" for clarity.
- Bounding box
- A conceptual mechanism for explaining rotation systems that allows depicting how orientations are positioned relative to one another.
- When the player clears the whole playfield without leaving any blocks behind. Also known as All Clear.
- The horizontal line separating the in-bounds rows of the playfield from the out-of-bounds rows. Most games place the ceiling at the top of row 20. In most games, the ceiling coincides with the top of the visible portion of the playfield.
- A unit square within the playfield.
- Placement of multiple consecutive pieces to clear lines.
- Delayed Auto Shift. Refers to the autorepeat of sideways movement.
- Downward movement of a piece.
- Entry delay
- Time between when one piece finishes and when the following piece enters.
- Falling piece
- The tetromino or other piece under the player's control.
- Fast drop
- Another name for soft drop.
- Firm drop
- Moving the piece straight down as far as possible and starting the lock delay.
- Floor kick
- Upward movement of a piece when it rotates against the floor of the playfield or other blocks.
- Period during which the sequence of rotation, movement, and gravity is executed, and the result is displayed. Video games in Japan and North America run at 60 frames per second.
- A unit of speed of one cell per frame. Refers most often to gravity; can also refer to DAS or soft drop speed. For example, when gravity is 20G, each piece falls so quickly that it instantly spawns on top of the playfield.
- Rows of blocks added to the bottom of the playfield at the start of the game or during the game.
- Ghost piece
- A marker in the playfield showing where the falling piece will land. Also known as Temporary Landing System (TLS).
- The automatic downward movement of a piece over time.
- The specification for how Tetris games made in roughly 2001 and later should operate.
- Hard drop
- Moving the piece straight down as far as possible and locking it immediately.
- Placing the falling piece in storage and moving the piece that was in storage (or next in line if no piece was in storage) to the top of the playfield.
- Initial Rotation System (IRS)
- A rule allowing the player to rotate a piece as it enters the playfield by pressing and holding a button during entry delay.
- A rule in which lock delay resets every time a piece is shifted or rotated.
- Jiznickery 
- A misdrop due to an inadvertent zangi-move. It happens in games with firm drop when the player drops a piece but does not wait long enough for the piece to lock before trying to charge DAS or input IRS for the next piece. The New Tetris was especially susceptible due to its lack of manual locking.
- Line clear
- Creation of a complete row of blocks with no holes after a piece locks. It disappears, and the blocks above the row move down.
- After a piece has landed on the floor of the playfield or on other blocks, it becomes part of the playfield and is no longer subject to the player's control. Or to cancel lock delay, causing a piece to lock immediately.
- Lock delay
- The time between when a piece lands and when it locks.
- See Lock.
- Lock Out
- To top out by locking a piece above the ceiling. 
- A term used by The Tetris Company for a playfield.
- A term used by The Tetris Company for a block; this sense is little used outside TTC.
- The "block creatures" in the games Tetris Worlds and Kids Tetris are also called Minos.
- In Japanese Sega Tetris/TGM parlance, the term is used as an abbreviation of "Tetramino", thus referring to the whole piece instead of a single cell. The term "block", however, is used more often.
- A misdrop is when a player accidentally drops a tetromino in the wrong place, or in the wrong orientation.
- Move reset
- Another name for Infinity.
- Next piece
- Alternate term for piece preview.
- The direction that a piece faces. The number of orientations in Tetris pieces may not always be equal to the number of geometric orientations a shape can take. Shapes like Z, S, and I which only has two orientations, or O, which has only one, can be treated as having four internal representations in some games, most commonly those that implement the Super Rotation System.
- A block or column of blocks extending from a wall of blocks over an empty cell or column. Overhangs are commonly used as a method of reordering piece placements when a player recieves undesirable tetromino sequences. In games where T-Spins are rewarded, overhangs may be used to set up a T-Spin.
- A set of blocks that moves as a unit.
- Piece preview
- A display area of the tetrion devoted to displaying the next pieces that will enter the playfield.
- A grid of cells into which pieces are placed.
- Random Generator
- A specific randomizer used in newer games that guarantees an even distribution of piece types. It consists of a bag with one of each of the seven tetrominoes.
- An algorithm that generates a sequence of piece types.
- At least four adjacent rows that are filled with blocks except for a single hole in the same column.
- To change a piece's orientation by turning it clockwise or counterclockwise, generally by 90 degrees.
- Rotating the tires
- Alternate term for a twist.
- Rotation system
- A rule specifying the orientation for each piece type and the movements (including wall kicks and floor kicks) when changing orientations.
- Alternate term for ghost piece.
- Moving a piece sideways.
- Placing a piece under an overhang by moving it sideways.
- Soft drop
- Moving the piece down faster than gravity, while still retaining control over it.
- Sonic drop
- A name for firm drop arising from the TGM community.
- Sonic lock
- A name for hard drop arising from the TGM community.
- Super Rotation System (SRS)
- A rotation system for tetrominoes used by games that adhere to the Tetris Guideline.
- Step reset
- Lock delay resets every time the falling piece moves downward.
- Temporary Landing System (TLS)
- Arika's name for the ghost piece.
- Effect of failure to adapt to different variations of a puzzle game, especially different rotation systems. (Coined by colour_thief as a portmanteau of "tetromino" and "jet lag".)
- Alternate term for tetromino used in Nintendo Power reviews of 8-bit Tetris games.
- Alternate term for tetromino allegedly used by The Tetris Company in the late 1990s.
- Alternate term for tetromino used by The Tetris Company as of Tetris Worlds.
- A term used by The Tetris Company for the game object that contains a playfield. Different tetrions may implement different variations of the game rules. (Not to be confused with treknobabble.)
- The Tetris Company's trademark for products implementing the Soviet Mind Game.
- The act of clearing four lines with one tetromino.
- Top out
- A piece reaches the top of the playfield and the game ends.
- A twist performed with the T tetromino that satisfies specific requirements.
- Placing a piece under an overhang by rotating it.
- Wall kick
- Sideways movement of a piece when it rotates against the floor of the playfield or other blocks.
- A term used in some older games for the playfield.
- Moving a piece downward, sliding it, and locking it.
- Term Correspondence Chart for Japanese terms
- TGM legend for more explanation of terms used with the TGM series