Os and Sphenoid

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

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

Sphenoid noun - Butterfly-shaped bone at the base of the skull.

Os and sphenoid are semantically related. You can use "Os" instead a noun "Sphenoid".