The building blocks of English

Affixes

sacr(o)-

Sacrum.

Latin (os) sacrum, literally ‘holy bone’—it was believed to be the nucleus on which the body would be resurrected at the Last Judgement.

The sacrum is a curved triangular element at the back of the pelvis, consisting of five fused vertebrae. The adjective relating to it is sacral, as in the sacral nerves or the sacral vertebrae (it can also refer to sacred rites or symbols); the adjective sacroiliac refers to the sacrum and the ilium (especially the sacroiliac joint, inflammation in which is sacroiliitis, see ‑itis), while sacrococcygeal relates to the sacrum and the coccyx together.