A commenter
points out that "scalar" doesn't match the term from linear algebra (I knew this) and suggests using "box" instead from an array of rank 0. I don't really want to use box because it differs from the usage in boxed array languages like J, and I don't think it properly conveys the idea that there can only be one thing in it. Maybe "site" would be better? "Frame" or "shell" might work but also have conflicts.