Hong or jiang () is a two-headed dragon in Chinese mythology, comparable with rainbow serpent legends in various cultures and mythologies.
Chinese has three "rainbow" words, regular hong 虹, literary didong 蝃蝀, and ni 蜺 "secondary rainbow".
Note that all these Chinese characters share a graphic element of hui "insect; worm; reptile; etc." (cf. tripled chong ), known in Chinese as Kangxi radical number 142 and loosely translated in English as the "insect radical". In traditional Chinese character classification, "radical-phonetic" or "phono-semantic" characters are statistically the most common category, and they combine a "radical" or determinative that suggests semantic field with a "phonetic" element that roughly indicates pronunciation. Words written with this 虫 radical typically name not only insects, but also reptiles, and other miscellaneous creatures, including some dragons such as shen "aquatic dragon" and jiao "flood dragon". Linguistic anthropologists studying folk taxonomy discovered many languages have zoological categories similar to hui 虫, and Brown coined the portmanteau word wug (from worm + bug) meaning the class of "insects, worms, spiders, and smaller reptiles". Following Carr, "wug" is used as the English translation of the Chinese logographic radical 虫.
The regular script Chinese character for hong or jiang "rainbow" combines the "wug radical" with a gong "work" phonetic. Both Qin dynasty seal script and Zhou dynasty bronze script elaborated this same radical-phonetic combination. However, the oldest characters for "rainbow" in Shang dynasty oracle bone script were pictographs of an arched dragon or serpent with open-mouthed heads at both ends. Eberhard notes, "In early reliefs, the rainbow is shown as a snake or a dragon with two heads. In West China they give it the head of a donkey, and it rates as a lucky symbol."
The 121 CE Shuowen Jiezi dictionary, the first Chinese character dictionary, described the seal character for hong 虹 "rainbow" as 狀似蟲 "shaped like a wug".