Many terminologies specifically occur in puzzle instructions. Starting from WPC 2017, definitions of some of them are explicitly stated at the beginning of Instruction Booklets. Most of the followings are from 2019 IB.
Adjacent Cells: Two cells are said to be adjacent if they share an edge. For example, in a square cell grid, two cells are adjacent if and only if they lie horizontally or vertically next to each other.
Touching/Neighbouring Cells: Two cells are said to be touching or neighbouring if they share at least a point. Adjacent cells are automatically touching.
Connected: A group of cells is said to be (inter)connected if for every pair of cells it is possible to find a path connecting the two cells which lies completely within the group, and which only travels from one cell to an adjacent cell in each step.
Regions: A region is a set of connected grid cells, which is typically marked by drawing the borders of the region bold (or sometimes by shading all the cells in the region). Regions may have holes unless otherwise noted.
Area / Size: The area or size of a region/shape is the number of cells that belong to it. Potential holes are not counted here.
Congruent: Two regions are said to be congruent if it is possible to find a sequence of movements (shifting, rotating and possibly reflecting) that transforms one of the regions exactly into the other.
Pentomino: A pentomino is a shape consisting of five connected cells in a square grid. There are twelve different pentominoes:
Pentominoes and their labels
Pentominoes are labelled with the letters shown here. In some puzzles these letters have actual meaning, usually when some letters are marked in the puzzle grid and the respective pentominoes must be placed there.
Similarly, there are five tetrominoes (seven, if reflected shapes are considered different), consisting of four connected squares, and 35 hexominoes, consisting of six connected squares.
Object Placement: There are various puzzles where the task is to place certain objects in the grid (often the size of one cell, like stars, sometimes larger ones). The rules regarding the location of these objects – in particular the possibility of touching – always refers to the underlying cells containing these objects in the solution, even if the graphics appear to leave a space between the objects and the cell boundaries.
Dissection: There are various puzzles where the task is to divide the grid into regions. Unless otherwise noted, the dissection must take place along the grid lines, and every cell must belong to exactly one region (i.e. there cannot be either overlaps or leftovers).
Drawing Lines: There are various puzzles where the task is to draw lines in the grid (loops, connections, etc). In some puzzles styles like Slitherlink, these lines must run along gridlines; in other puzzle styles like Masyu, they run through grid cells.
Loop: A loop is a closed and connected set of line segments, i.e. there are no open ends, and there cannot be two or more separate loop components. Note that the connection requirement is stronger than that of the underlying cells being connected.
In puzzles where lines through grid cells are to be drawn, it is customary to always draw them through the centre points of the respective cells. This means, for example, that a loop passing through a cell more than once will always hit itself (even though it would theoretically be possible to draw the lines such that they pass through different parts of a cell without touching itself). If there is a rule that no cell can be used more than once, this will then automatically imply that the lines cannot hit each other (or that the loop cannot hit itself).
Snake: A snake is a single path in the grid which travels through adjacent cells only. Snakes often use a special notation, such as shaded cells or circles with number sequences instead of line segments, although this is not always relevant for the respective puzzle style. Snakes are not allowed to “touch” themselves. This means, if two adjacent cells are used by the snake, the underlying snake path must directly connect the one cell with the other; if two (diagonally) touching cells are used by the snake, the underlying path must connect the two cells via adjacent cells without a detour. The same non-touching condition is also sometimes used for loops (e.g. Bosnian Road).
A snake and its representations
Length: The word “length” (for example of paths or contiguous cell groups) is not used with the same uniform meaning throughout the instruction booklet. Sometimes – typically in shading puzzles, as in Coral – the term refers to the number of cells; sometimes – typically in loop/path puzzles, as in Castle Wall – it refers to the number of steps from one end to the other, i.e. the number of cells minus one. Read the specific puzzle instructions (and check the example) to find out which one is the case.
Killer: Some regions in a grid is marked. The sum of the digits in each cage must equal the value given in the upper-left corner of that cage. Digits cannot repeat inside a cage.
Knapp Daneben: Literally "close miss" in German. This means that all given clues are off by exactly 1, i.e. the correct clue would be 1 higher or 1 lower than the number given in its place.
For example, this is Knapp Daneben Shikaku from WPC 2019 IB.
Example
Solution
Coded/Encrypted/Crypto: This means that the numbers have been replaced by symbols (typically letters); the substitution is such that same symbols correspond to same numbers, different symbols correspond to different numbers.
Note, however, that sometimes the substitution refers to single digits only, and sometimes it refers to multi-digit numbers – read the specific puzzle instructions to find out which one is the case.
Incomplete Information: In many puzzles, the potential position of clues is fixed, for example outside the grid or in certain marked cells. If such a position does not contain a clue, this means that the respective information is not given (rather than take the value 0).
Puzzle sizes: The instructions (for example “Enter numbers from 1 to 6 . . . ) always refer to the size of the competition puzzles. The examples often use smaller grids, smaller sets of shapes etc. Usually, this should be obvious; in some cases when this may not be the case we have explicitly mentioned a different size.
