The yellow card has a somewhat different meaning for fencing than it does for soccer.

In fencing, a yellow card is an official warning--not a "penalty" per se. The fencer who receives the yellow card is not penalized in any way other than the receiving of the card. If the fencer repeats that same offense (or any other offense that would warrant a yellow card) during the same bout, he will then receive a red card. Yellow cards do not carry over from bout to bout.

Yellow cards are only given for the less serious offenses--others carry with them the penalty of red card or black card for the first offence, with no yellow card given at all.

The most common things a fencer can do to earn a yellow card include falling down, weapons and equipment not working or conforming to regulations, turning his back on the opponent, causing contact (corps a corps) with the other fencer], and refusal to obey the referee.

See the Fencing Penalty Chart for more info.