Mainly refers to book moves or specific sequences of moves. Patterns or variations of specific move orders used in openings or middlegame. A progression route. Used almost synonymously with Variation

A new move that has not been played before

Reaching the same position through different move orders. Example: 1.d4 Nf6 2.c4 e6 3.Nf3 d5 = 1.d4 d5 2.Nf3 Nf6 3.c4 e6

A structure that reproduces an opening with colors reversed. For example, the Reverse Sicilian has White and Black's roles reversed while maintaining the same structure

An Arabic-derived word meaning arrangement, formation, or deployment. A typical position that frequently appears after following book moves in the opening. A branching point where players begin to devise their own plans

Changing the move order to ultimately reach the same position. Example: English Opening → Queen's Gambit. In a broad sense, includes Reversal of moves