A yaku is a pattern in the winning hand, or in the way it was won, that scores points. World Jan has 21 of them. Most come from geography: which countries and regions your three sets are made of. Below each one is its condition, an example hand where the shape matters, where the name comes from and how to go for it.
Every yaku the hand qualifies for adds up, and the score is the points × 100, paid by the other player. The three yakuman are worth 30 points each and replace every other yaku. A Globe can stand in for one tile in each set, and still counts for the geography yaku as the tile it replaces.
Any winning hand
The point every winning hand gets, so that even the plainest three sets pay something. In mahjong a hand needs at least one yaku to win; here the win itself is one.
When the CPU is close to tenpai, a plain fast hand that takes the point is better than a slow pretty one. Speed first, value when it comes for free.
You were in riichi (declared automatically when one tile away)
In riichi mahjong, declaring riichi is a bet that locks your hand. World Jan declares it for you the moment you are one tile away, and it still pays a point.
Since it costs nothing, there is no decision to make, only a consequence: once in riichi, every drawn tile that does not win is discarded for you. Reach tenpai with a wait on as many tiles as you can, because you cannot change it afterwards.
You won on your own draw
Winning on your own draw rather than on the CPU's discard. In self-play about six wins in ten are by tsumo, so this point is more common than Ron.
A wide wait makes tsumo come sooner. Waiting on a tile that has already been discarded twice leaves one copy in the wall; a Globe or a different tile may be the better wait.
You made no calls
No Pon and no Chi. The name is borrowed from mahjong, where a hand with no open melds is concealed and scores more.
A call usually saves you a turn or two and costs this one point. The Normal CPU calls only while it is still two or more tiles away and keeps the last step concealed; Hard calls for the last step too. Copy Hard when you are behind.
For each Route set
A country's 1, 2 and 3 together, a trip through one country. It is the easiest set to make: three different tiles of the same country, nine copies in play, instead of all three copies of a single tile.
Route is worth a point per set, so three of them pay three before Grand Tour is added. With only 3 copies of each tile, lean towards Routes whenever a hand could go either way.
All three sets are Routes (on top of Route)
All three sets are Routes: a tour of three countries. It stacks on top of the three Route points, so the shape alone is worth six.
Pick your three countries from one yaku group and the geography stacks too: three Routes from Peru, Chile and Mexico are Grand Tour, Pacific Rim, Ancient World and New World at once.
Two or more Triplets
Two or more Triplets in the hand. Triplets are rare, because a Triplet needs every copy of a tile, so two of them earn a bonus.
Only worth going for when the tiles are already in your hand; a Globe can complete the second Triplet. Pon on the CPU's discard is the usual way to get there.
Triplets of one country's 1, 2 and 3
Nine tiles of a single country: Triplets of its 1, its 2 and its 3. You never left home. One of the three yakuman.
Every copy of all three tiles must reach your hand, or Globes must fill the gaps, so it is mostly luck and Pon. If you hold two copies each of a country's three tiles, this is the hand to chase.
All nine tiles from one region
All nine tiles from one region, which on the table means all one colour. Every region has exactly three countries, so the hand is three sets from those three.
Three Routes from the three countries of one region is One Region plus Grand Tour plus Old or New World. Look at the colours in your starting hand before anything else.
Three Triplets of the same number
Three Triplets all of the same number: three 1s, three 2s or three 3s. One of the three yakuman, and the hardest, because Triplets are hard and here all three must match.
Practically a gift of the deal. If you start with pairs of the same number from two countries, keep them and Pon what the CPU throws; a Globe can finish one of the sets.
Every set from Japan, the United Kingdom or New Zealand
Every set from Japan, the United Kingdom or New Zealand, the three island nations in the game. One of the three yakuman, and the only one you can reach with Routes.
Three Routes from the three islands is enough. Watch for the three colours: Japan is Asia, the UK is Europe, New Zealand is the South Pacific, so the hand looks mixed until you notice the islands.
Every set from Asia, Europe or Africa
Every set from Asia, Europe or Africa, the continents known before the voyages of the fifteenth century. Nine of the eighteen countries belong to it.
Half the tiles qualify, so Old World often arrives by itself. Its mirror image is New World; a hand can never be both, so once two sets agree, discard the odd continent.
Every set from the South Pacific or the Americas
Every set from the South Pacific, North America or South America. The other nine countries, the other half of the tiles.
Pairs naturally with Pacific Rim, since eight of the nine New World countries face the Pacific. Only Brazil does not, so a New World hand without Brazil is usually a Pacific Rim hand as well.
Every set from a country on the Pacific
Every set from a country with a Pacific coast: ten of the eighteen, from Japan round to Chile. The widest of the geography yaku.
The easiest group yaku to complete, and it combines well: add Natural Wonders with Japan, New Zealand and Canada, or Ancient World with China, Mexico and Peru.
Every set from the southern hemisphere
Every set from the southern hemisphere, named for the constellation on the flags of Australia, New Zealand, Papua New Guinea and Brazil. Seven countries qualify.
Worth two points, and the South Pacific's three countries alone give it along with One Region. South Africa is the odd one out: it is the only Southern Cross country that is not also Pacific Rim or New Seven Wonders.
Every set from Egypt, China, Italy, Mexico, Peru or Chile
Every set from Egypt, China, Italy, Mexico, Peru or Chile, the countries whose landmarks were built by ancient civilisations: the pyramids, the Great Wall, the Colosseum, Chichen Itza, Machu Picchu and the moai.
Three points, and three of its six countries (Mexico, Peru, Chile) are also Pacific Rim, so an Americas hand often gets both. Egypt, China and Italy give Ancient World plus Old World instead.
Every set from the New 7 Wonders in the game
Every set from the New Seven Wonders of the World voted in 2007: the Great Wall, the Taj Mahal, the Colosseum, Chichen Itza, Christ the Redeemer and Machu Picchu. The seventh, Petra, has no tile.
Three points for a hand from six countries. Mexico, Brazil and Peru give it with New World; China, India and Italy with Old World. Brazil is the key tile: among the country groups it belongs only to this one and Southern Cross.
Every set from Japan, New Zealand, South Africa or Canada
Every set from Japan, New Zealand, South Africa or Canada, the four landmarks shaped by nature rather than built: Mount Fuji, Mitre Peak, Table Mountain and Niagara Falls.
Three points from only four countries, so it needs some luck, but three of the four are Pacific Rim as well. A hand of Japan, New Zealand and Canada Routes is Natural Wonders, Pacific Rim and Grand Tour together.
No Globe in the hand
No Globe in the hand. Globes make winning easier, so a hand that did without them is paid three points. With 4 Globes in the wall, roughly a quarter of wins use one.
Do not refuse a Globe for the sake of Pure: a win now beats three points later. But when a Globe would only replace a tile you are about to draw anyway, keep the hand pure.
You won within 6 turns
Winning within 6 turns, counting your draws and calls. A hand that was nearly complete from the deal, or finished with quick calls.
You cannot plan it, but Pon and Chi count as turns like draws, so a quick call does not spoil it. A starting hand with two sets already made is an Express candidate.
The dealer wins a repeated hand
The dealer wins a hand that is being replayed because the dealer won or was tenpai the time before. Mahjong players know it as a dealer repeat, honba.
A point for keeping the seat. As dealer, a fast win sets up a renchan hand where the next win pays extra; as the other player, breaking the repeat is worth a quick cheap hand.