In the anatomical word coccyx ('the lower end of the spinal column in humans', analogous to the tail in many other vertebrates), the two central '-c-'s are pronounced separately, the first like a '-k-' and the second like an '-s-'. The stress is on the first syllable. The whole is 'COCK-six', IPA: /'kɒksɪks/.
- The coccyx exists in humans and the great apes ('the tail-less apes'), birds (in which the tail feathers are attached to the coccyx) and some other vertebrates. It is formed by the fusion of the lower vertebrae, between three and five but usually four in humans. In less formal English, it is known as the 'tail-bone' or the 'rump-bone'.
The plural, in British English, is coccyxes ('COCK-sixes'), which follows Latin usage. Americans say 'coccyges' (cock-SIGH-jeez', IPA: /kɒk'saɪdʒiːz/), which is closer to the original Greek form: κόκκυξ (coccux) in the singular, κοκκύγες (coccuges) in the plural. The Greek word means 'the cuckoo bird', but was also used by medical writers with the same meaning as the English 'coccyx'. 'Coccyx', the Latin transliteration of the Greek word, was used by the Romans simply to mean 'cuckoo'; it was applied to the bone in the seventeenth century, because anatomists fancied that the bone resembled a cuckoo's beak.