Chess clock glossary

Time-control terms

Base time is the amount each player receives before any bonus. Increment adds a fixed number of seconds after a completed move. Simple delay protects the opening seconds of a turn before the main bank falls. A stage adds time after a stated move number. The written control must identify which of these rules applies.

Display and button terms

The active side is the timer currently counting down. A flag indicator records that a player's time reached zero; on a mechanical clock, a physical flag falls. Pause stops both sides without clearing them. Reset returns the clock to its starting state, while a move counter records presses or completed turns depending on the device.

Tournament terms

An arbiter is the official responsible for applying event rules. Default time is the latest permitted arrival under that event's regulations. A time-forfeit claim asks for a result after a flag fall, but the board position and governing rules still matter. Never recreate a disputed display from memory.

Source for the factual guidance above: FIDE Laws of Chess.

Use the term that matches the setting

Bonus is a broad label, not a precise timing method. Say increment, simple delay or Bronstein timing when that distinction matters. Write 10+5 only when the plus notation is defined as increment; a schedule or clock manual should spell out any staged or unusual control.

Worked notation examples

In 5+0, each player starts with five minutes and receives no increment. In 3+2, each starts with three minutes and gains two seconds after every completed move. In a ten-minute game with a five-second simple delay, the main bank waits for the delay before decreasing and cannot grow from unused delay. A staged control must also state the move threshold and time addition. These examples show why the numbers alone are not always enough: the timing method is part of the control.

Terms that are often confused

Flag fall means the clock recorded expiry; it is not a synonym for checkmate. Increment adds a fixed amount after a move, while simple delay postpones the decrease of the main bank. Bronstein timing returns up to a limit after the move and may look different on the display. A move counter usually counts presses, but a press is not guaranteed to equal a legal completed move. Default time concerns permitted arrival at an event, not the initial number displayed on the clock.

How to describe a clock problem

Use observable details instead of a conclusion. Say, 'White shows 4:21, Black shows 4:35, the Black side is running, and the flag icon is beside White,' rather than, 'The clock stole time.' Identify the model or browser, selected control, bonus mode, and action immediately before the problem. Note whether the device was paused, reset, rotated, or interrupted. Precise terms let an organizer, opponent, or support person distinguish a setting error from a display misunderstanding or genuine device fault without rewriting the game from memory.