There are a variety of different counters, with different types having different names, such as Spell Counters or Greed Counters. Some cards use counters that are simply named "counter", such as "B.E.S." monsters.
There is no official way to represent a counter. However, some of the most common ways include small objects like glass beads, paper clips, pennies/coins, or the numbers on a die.
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Counter (collectible card games).
Counters themselves do not have effects, although cards that place counters can apply an effect to a card as long as it has a counter (such as cards that place Cubic Counters and Predator Counters).
Counters that can only be placed on the card that places them, as well as counters that can only be placed on specific cards (such as Spell Counters), can only remain on a card as long as that card's effects are applying. If a card's effects are negated, all such counters are removed from it.
- Konami. Yu-Gi-Oh! Official Card Game - Perfect Rulebook 2017. pp. 171–172.