How useful are terminal tiles in Japanese mahjong?
An advanced riichi mahjong strategy guide series
Tile efficiency is key in winning any mahjong game. This is even more so in Japanese mahjong, as there are clear advantages of keeping your hand closed throughout the game. First, it allows you to call riichi, which is worth at least 1 Han, and an opportunity to get Ura Doras and Ippatsu which can further increase the value of your existing hand. Secondly, it helps in defensive play to guard against players who called riichi, as you will have more tiles available to discard. Hence, although open hands (by calling “chii” or “pon”) can win a hand more quickly, winning with closed hands secures higher winning points.
In this blog entry, we will zoom into looking at the value of terminal tiles, which are the 1 and 9 sou (bamboo), 1 and 9 man (characters), 1 and 9 pin (circles). The question is we will be addressing is: In what circumstances should we keep or discard them?
What is the value of terminal tiles in comparison to other tiles? Let’s consider a specific example of 9 sou:
A victory in mahjong is made of 4 groups of 3 tiles and 1 pair. Hence, if you have one copy of 9 sou with no other neighbouring tiles, you will need to draw a neighbouring tile (7, 8 or 9 sou in this case) as a partner, so that you can eventually meld into a group of 3 tiles. That makes a total of 11 possibilities to draw from the pile. However, an important point to note is that even if you fortunately draw 7, 8 or 9 sou, the outcome will be a one-sided or edge wait, which is a bad wait. For instance, if you draw 7 sou, then you can only wait for 8 sou to form a group of 3. Similarly, if you draw 8 sou, you can only wait for 7 sou to form a group of 3. Due to these above reasons, terminal cards are often not favoured, especially if there are no other neighbouring tiles in your hand.
You may now be confused. If you have followed my previous posts on Dragon and wind tiles, we know that we should discard these tiles first when we have only 1 copy. Based on the argument above, terminals seem to be low value as well, especially when not paired or surrounded by neighbouring tiles. So if we have both honours and terminal tiles, which one should we discard first? Let’s analyse the value of the cards rationally.
If we calculate based on probability, the chances of drawing neighbouring partner tiles (11 possibilities) is much higher compared to honours tiles (3 possibilities). Hence, if we are striving for tile efficiency, terminals have a higher chance of forming a group of 3 compared to honours tiles. However, if we calculate based on value, then honours tiles are worth an additional 1 Han (ignoring the wind tiles that are 0 Han) as compared to terminal tiles. So, should we sacrifice value for tile efficiency?
My answer is no, but there is one exception…
One reason is because the chances of getting a partner for a terminal tile is about 3–4 times higher compared to the honours tile. In addition, although honours tiles are worth more at face value, the low probability of drawing the same copies usually means that we will have to “pon” to meld a triplet. This will compromise our chances of riichi, which can potentially be worth more than 1 Han.
However, there is an exception to consider. Consider you have a both a 9 sou and 6 sou in your hand. Now, the value of the 9 sou depreciates substantially because drawing 7 or 8 sou can be paired with 6 sou, meaning that:
1. You will have to draw 2 copies of 7 or 8 sou to be able to pair with both the 6 and 9 sou
2. You draw 9 sou (only 3 possibilities) to potentially meld into a triplet
The value of 9 sou in this case is lower as compared to honour tiles. This is because you only have 3 possibilities to form a pair with 9 sou, and you can’t call a “pon” even if you successfully draw a 9 sou pair! Moreover, terminal tiles are usually much more dangerous to keep than honour tiles when someone calls a riichi, as ~50% of players who call riichi prefer to have a 2 sided wait for Pinfu.
Based on the above justifications, the rational decision to discard honours tile or terminal tiles first will depend on the other tiles in your hand. If you have a 9 suit and a 6 suit, you should discard the 9 suit first. Similarly, if you have a 1 suit and a 4 suit, you should discard the 1 suit first. Otherwise, the honour tiles should be discarded earlier.
In summary, prioritise keeping terminal tiles when:
1. Terminal tiles are Dora tiles
2. Aiming to form half outside hand, full outside hand, straight hand or mixed triple sequence
3. You have a pair, which can serve as “eyes”
Discard terminal tiles when:
1. You have a 1–4 or 6–9 combination in your hand.
2. You have other more efficient tiles, including middle tiles, red tiles or Dora tiles.
3. There are no other safe cards to discard.
4. Terminal tiles are Suji-pai. This means that if a player calls riichi and throws a 4 or 6, they are one of the safest tiles to discard as they do not have a 2–3 pair or 7–8 pair respectively. Will likely cover this more in my later posts.
So that’s it for my perspective on terminal tiles. This article is written with feedback from Kuan Chuan Chan. Stay tuned for more mahjong strategy articles!
Kuan Rong Chan
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