Thin Space

The Thin Space at U+2009 is an invisible spacing character that inserts a narrow blank gap, typically about one fifth of an em, between neighboring characters. It is part of the General Punctuation block and belongs to Unicode’s space separator category, so it behaves as whitespace while being visibly slimmer than an ordinary word space. Its most common role is fine typography. Publishers use it where a normal space looks too wide but no space feels cramped, such as around certain punctuation, between grouped initials, or in tightly set abbreviations. In French-style typography, a thin space is often used before high punctuation such as a semicolon, question mark, or exclamation mark when precise spacing is available. It also appears in mathematics, science, and technical writing as a separator that improves readability without strongly dividing terms. Examples include spacing between a number and a unit, as in 25 °C or 10 kg, grouping large numbers as 12 345, or separating adjacent factors in formulas. The practical gotcha is that it is easy to miss during editing: searches, line breaking, and data cleanup may treat it differently from a regular space, so copied text can behave unexpectedly.