coccyx

American  

[kok-siks] / ˈkɒk sɪks /

noun

plural

coccyges

1. a small triangular bone forming the lower extremity of the spinal column in humans, consisting of four ankylosed rudimentary vertebrae.

2. a corresponding part in certain animals.

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coccyx British  

/ kɒkˈsɪdʒɪəl, ˈkɒksɪks /

noun

1. a small triangular bone at the end of the spinal column in man and some apes, representing a vestigial tail

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coccyx Scientific  

/ kŏk′sĭks /

plural

coccyges

1. A small triangular bone at the base of the spine in humans and apes. It is composed of several fused vertebrae.

2. Also called tailbone

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Other Word Forms

• coccygeal adjective
• intercoccygeal adjective
• precoccygeal adjective

Etymology

Origin of coccyx

1605–15; < New Latin < Greek kókkyx cuckoo, from its resemblance to a cuckoo's beak

Compare meaning

How does coccyx compare to similar and commonly confused words? Explore the most common comparisons:

• sacrum vs. coccyx

Example Sentences

The boy was fifteen, skinny, almost malnourished, so that the hip bones and coccyx stood out sharply.

From The Wall Street Journal • Nov. 11, 2025

Following this evolutionary split, the group of apes that includes present-day humans evolved the formation of fewer tail vertebrae, giving rise to the coccyx, or tailbone.

From Science Daily • Feb. 28, 2024

The pelvic diaphragm, spanning anteriorly to posteriorly from the pubis to the coccyx, comprises the levator ani and the ischiococcygeus.

From Textbooks • Jun. 19, 2013

The vertebral column originally develops as 33 vertebrae, but is eventually reduced to 24 vertebrae, plus the sacrum and coccyx.

From Textbooks • Jun. 19, 2013

This fasciculus, long and narrow, takes origin from the summit of the sacrum, or the coccyx, and goes to partake of the femoral insertions of the muscle which it accompanies.

From Artistic Anatomy of Animals by Cuyer, ?douard