The English language makes a distinction between blue and green, but some languages do not. Of these, quite a number, mostly in Africa, do not distinguish blue from black either, while there are a handful of languages that do not distinguish blue from black but have a separate term for green.[1] Also, some languages treat light (often greenish) blue and dark blue as separate colors, rather than different variations of blue, while English does not.
Many languages do not have separate terms for blue and green, instead using a cover term for both (when the issue is discussed in linguistics, this cover term is sometimes called gruein English). For example, in Vietnamese both tree leaves and the sky are xanh (to distinguish, one may use xanh lá cây ”leaf grue” for green and xanh dương ”ocean grue” for blue). In the Thai language, เขียว (khiaw) means green except when referring to the sky or the sea, when it means blue; เขียวชอุ่ม (khiaw cha-um), เขียวขจี (khiaw khachi), and เขียวแปร๊ด (khiaw praed) have all meant either intense blue or garish green, although the latter is becoming more usual as the language ‘learns’ to distinguish blue and green. Chinese has a word 青 (qīng) that can refer to both, and sometimes black, though it also has separate words for blue (蓝 / 藍, lán), green (绿 / 綠, lǜ), and black (黑, hēi). The Korean word 푸르다 (pureuda) can mean either green or blue. In Japanese, the word for blue (青 ao) is often used for colors that English speakers would refer to as green, such as the color of a traffic signal meaning “go”. Some Nguni languages of southern Africa, including Tswana utilize the same word for blue and green.
The exact definition of “blue” and “green” may be complicated by the speakers not primarily distinguishing the hue, but using terms that describe other color components such as saturation and luminosity, or other properties of the object being described. For example, “blue” and “green” might be distinguished, but a single term might be used for both if the color is dark. Furthermore, green might be associated with yellow, and blue with black or gray.