Hole - one of the playable locations on the 24x24 grid of board positions. The four corner locations on the 24x24 grid are not playable.
Border Row - A row (or column) of holes along an edge of the board.
The white border rows are along the "top" and "bottom," and the black border rows are along the left and right edges. Some sets may use different colors -- most often red and black. Most boards have a colored bar separating the border rows from the rest of the grid.
Peg - the game piece used to claim a location on the grid. A peg may be placed in one of the holes to occupy it.
Link Piece - the game piece used to connect two pegs on the board.
Link - two pegs joined together by placing a link piece with an end on each peg. The two pegs are separated by a single hole on one axis and two holes on the other (like a knight's move in chess). This is the next most basic move besides placing a peg. A peg can be linked to another peg placed in any of eight other surrounding holes, as illustrated.
Generally, when an article on Twixt uses the term "link" the definition of link as given here is what was intended. However, "link" is sometimes used to mean link piece as defined here (for example, in the official rules). It is not uncommon to find link used in both ways within the same article, leaving the interpretation to be determined by the reader based on context.
Setup - two pegs not joined but where there are two possible ways to join them by placing a single peg and connecting two or more links.
Setups can be: unanchored (no link on either side), singly anchored (only one of the two pegs having a link) or doubly anchored (both pegs having a link). Unanchored setups are much easier to "break", while setups anchored at both ends are (usually) nearly impossible to break.
There are three basic setups with two variations. It is important to be familiar with all of them. The square setup is exactly that and looks the same no matter which way you look at it. Then there is a skinny diamond setup and a normal diamond setup. A normal diamond setup is also called a beam setup when set up from the long end points.
In the figure to the right, c3 and f4 create a square setup, and either e2 or d5 could complete the connection. A skinny diamond setup is created by c7 and f4, and could be completed by either d5 or e6. Finally, a normal diamond or beam setup is created by c7 and c3, and could be completed by either b5 or d5.
As illustrated in the figures below, each of these setups can be established using either the long or the short axis:
In the case of the symmetrical square setup, either of the two equal axes may be used:
A simple setup is two pegs that could be joined by a single link, but are not. This could occur if a player had removed a previous link or, for some reason, had never placed it.
Bridge - a setup that has been completed.
Cardinal Lines - Straight lines that start in a corner of the board and continue all the way to an opposite side of the board along a series of holes that could be connected with links. There are two cardinal lines originating from each corner. Cardinal lines are also sometimes called help lines.
Definitions contributed by Steven Medcalf; edited and adapted (with some additions derived from the rules) by Peter Eirich.