Green Dragon

Did you know

• It is the youngest of the honors. The oldest surviving sets, from around 1872, don't have it; by around 1890 it had arrived, probably in Ningbo.²³¹
• 發 means to shoot or send off. On a Ningbo set from around 1890 it is drawn with a bow on the left and an arrow on the right, which fits the archery reading of the dragons.³⁴
• Japanese players also call it 緑發 ryūfa, and score sheets write it R. A Chinese nickname: 周潤發, the actor Chow Yun-fat.⁵⁶
• It is the only honor that can go into ryuuiisou, the all-green yakuman. In Mahjong Soul rules it isn't required there.

At the table

• Honors never make sequences. Green dragon can only be used in a pair, a triplet or a kan, so a lone one is often the first tile out of a hand.
• It is dora when is the dora indicator. Turned up as the indicator itself, it makes dora.

Yaku it can help

• Yakuhai a triplet is 1 han
• Shousangen two dragon triplets and a dragon pair
• Daisangen all three dragon triplets
• Honitsu one suit plus honors
• Tsuuiisou honors only
• Chanta a terminal or honor in every set
• Honroutou terminals and honors only
• Kokushi Musou one of the thirteen orphans
• Ryuuiisou the green tiles only

Where the dragons come from

The dragons came together late. The oldest surviving sets, brought from China around 1872, have 中 filed with the winds and eight blank tiles, but no 發. By around 1890, sets from Ningbo came in boxes marked 中發, the game's name at the time, which the British consular official Wilkinson, who bought them, glossed as "hit and go". Dragons is Babcock's English name from the 1920s; in Chinese they are 三元牌, the "three fundamental tiles".²³¹

Nobody knows for sure what the three stand for. One reading is archery: 白 the white target, 發 loosing the arrow, 中 hitting it. Another sees life's three prizes: 發 wealth, 中 a marriage, 白 a spotless name. A Japanese folk reading sees a beauty: white skin, glossy black hair (in Japanese, midori no kurokami, "green-black hair"), red lips. Japanese players list them in that order, haku, hatsu, chun; Chinese says 中發白.⁴⁶

They also gave Japanese mahjong a word: dora, the bonus tiles, is short for the English dragon.⁷

Sources

1. Mahjong tiles, Wikipedia
2. 二 一九世紀の中国麻雀牌（プロト・マージャン）, p. 2: グロバー牌 (the Glover sets, c. 1872), Japan Playing Card Museum (日本かるた文化館) Japanese
3. 二 一九世紀の中国麻雀牌（プロト・マージャン）, p. 5: ウイルキンソン牌 (the Wilkinson set, Ningbo, c. 1890), Japan Playing Card Museum (日本かるた文化館) Japanese
4. 【現代麻雀への道】41 三元牌の意味は？, Fukuchi Makoto, note Japanese
5. 麻雀牌, Wikipedia (Japanese) Japanese
6. 麻雀牌, Wikipedia (Chinese) Chinese
7. ドラ (麻雀), Wikipedia (Japanese) Japanese