⟨NBSP⟩
The space that holds two neighbors on the same line — Fig. 7 never parts again.
The size of an ordinary space, but welded: the line will not break over it. It is the gem for pairs that make no sense apart — Fig. 7, 10 km, Elizabeth II.
It is probably the most typed entity on the web, — and the most abused, stacked up to fake indentation. Its true trade is another: keeping together the pairs a line break would separate.
Wrong: article 5 split: “article” at the end, “5” orphaned on the next line
Right: article 5 — number and word cross together