Os and Pubis

Os noun - A hard brittle blue-grey or blue-black metallic element that is one of the platinum metals; the heaviest metal known.

Pubis and os are semantically related. In some cases you can replace term "Pubis" with "Os", this nouns are similar.

Pubis noun - One of the three sections of the hipbone; together these two bones form the front of the pelvis.

Os and pubis are semantically related. You can use "Os" instead a noun "Pubis".