The plural of cranium is craniums or crania.
The cranium is the bony structure that encloses and protects the brain and sensory organs in the head of humans and other vertebrates. It is the part of the skull that forms the upper portion of the skullcap, providing support and structure for the brain and serving as a protective covering.
The graph shows the occurances of the plural of cranium in written English since 1800 using Google's Ngram Viewer.
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