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

Around the age of 70, the sacrum and the coccyx may fuse together.

From Textbooks • Jun. 9, 2022

This large opening is defined by the inferior margin of the pubic symphysis anteriorly, and the ischiopubic ramus, the ischial tuberosity, the sacrotuberous ligament, and the inferior tip of the coccyx posteriorly.

From Textbooks • Jun. 19, 2013

At its inferior, or lower angle, it is united to the coccyx.

From A Treatise on Anatomy, Physiology, and Hygiene (Revised Edition) by Cutter, Calvin