Karaten

Example of a karaten riichi, with all waiting tiles circled in red.

Karaten 「カラテン」, or empty tenpai, is a state where a tenpai hand does not have the ability to win. This is due to unavailability of all instances of winning tiles. The "visible tiles" may either be discarded, used as a dora indicator, or already exist in one's hand. Furthermore, they may be held in other player's hands or even reside within the dead wall. However, the latter case is beyond a player's visibility.

The fifth tile case

Karaten tenpai acquired after calling kan.

The term is often confused with the "fifth tile" case. Here, a hand waiting for a fourth tile that is simply hidden, discarded, or used by someone else remains a valid tenpai in all circumstances. A hand may contain a 1-2 penchan and a previously declared kan of 3-3-3-3 in the same suit. This renders the threes unavailable as winning tiles. Some platforms would consider this case as tenpai, while others may deem it as noten. As always, this depends on the rule variations.

Example:
Waiting for:

Quirks

• On Ron2, there has been an instance of a person being able to call riichi with a gutshot wait shape for a 6-pin when they have made a closed kan of 6-pin already. The hand was considered noten, but did not trigger a chombo penalty (mainly due to programming assuming no one could do something that could be viewed as faulty). The hand was not in a valid tenpai shape when it came to scoring a drawn hand, but not okay for determining if a player was legally allowed to declare riichi.
• On Tenhou, there have been reports of a hand containing 12s44466688p with a kan of 3s, scored as in tenpai. Likewise, the same kind of case is allowable in Mahjong Soul.