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The modern English word blue comes from Middle English bleu or blewe, from the Old French bleu, a word of Germanic origin, related to the Old High German word blao.[2] In heraldry, the word azure is used for blue.[4]
In Russian and some other languages, there is no single word for blue, but rather different words for light blue (голубой, goluboy) and dark blue (синий, siniy). See Color term.
Several languages, including Japanese, Thai, Korean, and Lakota Sioux, use the same word to describe blue and green. For example, in Vietnamese the colour of both tree leaves and the sky is xanh. In Japanese, the word for blue (青 ao) is often used for colours that English speakers would refer to as green, such as the colour of a traffic signal meaning "go". (For more on this subject, see Distinguishing blue from green in language)