Basic Color Terms

Basic Color Terms: Their Universality and Evolution is a book by Brent Berlin and Paul Kay. Berlin and Kay's work proposed that the basic color terms in a culture, such as black, brown, or red, are predictable by the number of color terms the culture has. All cultures have terms for black/dark and white/bright. If a culture has three color terms, the third is red. If a culture has four, it has either yellow or green.
Berlin and Kay posit seven levels in which cultures fall, with Stage I languages having only the colors black and white. Languages in Stage VII have eight or more basic color terms. This includes English, which has eleven basic color terms. The authors theorize that as languages evolve, they acquire new basic color terms in a strict chronological sequence; if a basic color term is found in a language, then the colors of all earlier stages should also be present. The sequence is as follows:

Stage I: Dark-cool and light-warm
Stage II: Red
Stage III: Either green or yellow
Stage IV: Both green and yellow
Stage V: Blue
Stage VI: Brown
Stage VII: Purple, pink, orange, gray or silver

The work has achieved widespread influence. However, the constraints in color-term ordering have been substantially loosened, both by Berlin and Kay in later publications and by various critics. Barbara Saunders questioned the methodologies of data collection and the cultural assumptions underpinning the research, as has Stephen C. Levinson.
One concern is whether the concept requires too much discretion when deciding what counts as a "Basic" color term, or which color divisions count as essentially the same. This raises several open questions:
Should light blue/azure be included with the stage VII color terms, even though it isn't basic in English? Is "orange" truly a "basic" term in English, and if so, is the selection of which terms are basic influenced by either the theory or historical accidents of European cultures? Are these color divisions for Gaelic or the Himba people fully compatible with the dark/light, then red, then yellow and green, then blue expectation?
File:Colours in Irish.png|thumb|left|Color wheel with Irish Gaelic color terms, explaining that glas and gorm are distinguished based on intensity rather than hue. Similarly, buí refers not only to "yellow" and "gold", but pale browns as "buff beige" and "ochre", while dunn is for darker browns. Rua refers to red of hair, whereas dearg refers to red of blood and bándearg is "pale red". Then, Bán, fionn, geal, and liath all refer to varying degrees of brightness or "fairness" — without mapping clearly only the English "white" — against dubh for "dark" or "black".