Chess-family games share one irreducible core: check—a clear, verifiable exposure of a terminal piece to immediate capture. Boards, piece sets, promotions, drops, and scoring may change; the constant is that a public threat creates a debt: answer it, or accept that the story is effectively told.

From this vantage, check is the game's language of inevitability. A terminal piece—often a king, sometimes several, sometimes more abstract—has fallen within the opponent's immediate reach. The side under threat must dissolve it by whatever means the variant permits: movement, interception, counter-pressure, or other mechanisms native to that tradition.

Three archetypal routes to finality

There are three archetypal routes by which the game reaches its conclusion:

1. Checkmate: the threat stands and cannot be defused. The terminal piece is exposed to capture, and every possible continuation leaves it exposed. Capture follows in the next moment, whatever is attempted.
2. Stalemate: the terminal piece is not yet threatened, but every possible continuation would create that exposure. Any path forward ushers in capture. The side to move can preserve safety only by not moving—yet must move.
3. Staleturn: the side to move has no available continuation at all. True gridlock—not constrained by the threat of exposure, but by pure mechanical impossibility. Every piece is blocked according to its movement capabilities.

The horizon of inevitability

Adjudications differ across traditions (win, draw, special outcomes), yet these routes point to a single horizon: the inevitability—or impossibility—of continuing without conceding capture.

In checkmate, the threat exists and cannot be dissolved. In stalemate, safety exists but cannot be maintained through any move. In staleturn, movement itself has ended. Each represents a different form of checkmate: immediate, prospective, or mechanical.

The custom of resignation

Hence the near-universal custom: resignation. It is not mere courtesy but recognition. Once inevitability (or immobility) is plain—whether the threat already stands or would arise from any move—there is no need to enact the sequence for both players to know the last line. The board has already said enough.

Related resources

For a rule-agnostic framework that captures these observable states across chess variants and traditions, see the Chess Game Status Notation (CGSN) specification at sashite.dev/specs/cgsn/. CGSN provides standardized identifiers like checkmate, stalemate, and staleturn that separate observable facts from competitive interpretation.