- S
- In algebraic chess notation, the letter N is usually used to indicate the knight. In chess problems, however, the letter S (standing for Springer, the German name for the knight) is often used instead, with N instead being reserved for the popular fairy piece, the nightrider.
- Selfmate
- A type of problem where white forces black to mate him against black's will within a specified number of moves.
- Seriesmover
- A problem in which one side makes a series of moves without reply.
- Set play
- Play which is possible from the initial position of a problem if the other player moves first. For example, in a directmate, set play consists of lines of play starting with a black move (rather than a white move). When set play exists, the key move may be something which does not change the set play lines, in which case the problem is a complete block, or the lines in the set play may change, in which case the problem is a mutate. Set play is one phase of play.
- Solus rex (or Rex solus)
- When either color (though usually black) has only their King piece left. The term is derived from Latin and literally means "lone king."
- Switchback
- A piece leaves a square, and then later in the solution returns to it by the same route (for example, a rook moves e3-e5-e3). Compare with round trip, in which the route taken back to the original square is circuitous.
Read more about this topic: Glossary Of Chess Problems