# Thin space

A thin space is a blank typographic unit equal to one-fifth (sometimes one-sixth) of an em wide. Not to be confused with a narrow no-break space. The narrow no-break space is often used as an unambiguous thousands separator. It is also used to add space to nested quotation marks.

In Unicode, thin space is encoded at U+2009 thin space (HTML `&#8201;` · `&thinsp;`). Unicode's U+202F narrow no-break space is a non-breaking space with a width similar to that of the thin space. In HTML, a narrow non breaking space may be written as `&#8239;`.

In LaTeX and Plain TeX, \thinspace results in a narrow no-break space.[1] \, works the same way outside math formulas with LaTeX, while inside math formulas it works like a breakable narrow space.[2] In Plain TeX, `\,` throws in error outside math formulas and, as in LaTeX, produces a breakable narrow space inside math formulas.[3]

In Microsoft Word and other word processors, within the symbol dialog (often available via Insert > Symbol or Insert > Special Characters), both the thin space and the narrow no-break space are available for point-and-click insertion. In Word's Symbol dialog, under font = "(normal text)", they are found in subset = "General Punctuation".

A hair space is even thinner than a thin space, while a zero width space has no width at all.

1. ^ For Plain TeX, see D. E. Knuth: The TeXbook, Addison Wesley, Reading, Massachusetts, 1984 and later, p. 5 as well as p. 352. The reason is that both in Plain TeX and in LaTeX,`\thinspace` is defined as a `\kern`, at which a line cannot be broken, see The TeXbook, p. 75, and J. Braams and others: The LaTeX 2ε Sources (PDF, 2.3MB), 2011/06/27, p. 65.
2. ^ `\,` essentially is defined as `\ifmmode\mskip\thinmuskip\else\thinspace\fi`, so it results in an `\mskip` which produces glue, The TeXbook p. 290 and chapter 12.