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Solidus (punctuation)

The solidus ( ⁄ ) is a punctuation mark that is not found on standard keyboards. It may also be called a shilling mark or in-line fraction bar. Its Unicode encoding is U+2044.

The solidus is similar to another punctuation mark, the slash, which is found on standard keyboards; the slash is more nearly vertical than the solidus. These are two distinct symbols that have entirely different uses. However, many people do not distinguish between them, and when there is no alternative it is acceptable to use the slash in place of the solidus.

Typographers should note that both the ISO and Unicode designate the solidus as “FRACTION SLASH” ^[1] and the slash as “SOLIDUS.” ^[2] This contradicts long-established English typesetting terminology. ^[3]

History

The names solidus and shilling mark have the same background. In the Commonwealth of Nations, before decimalisation, currency sums in pounds, shillings, and pence were abbreviated using the '£' symbol, the 's.' symbol, and the 'd.' symbol — collectively £sd — referring to the libra, the solidus, and the denarius. The 's.' was written using a long s, ∫ that was further abbreviated to the ⁄ symbol, and suppression of the 'd.'; thus '2 pounds, 10 shillings, and 6 pence', written as £2,10⁄6 (instead of '£2, 10s. 6d.'), and '6 shillings' would be written as 6 ⁄-. This usage caused the names solidus (given the abbreviation's historical root) and shilling mark to be used as names for this character.

Usage

Currency

The shilling mark is used to denote shillings, see the History section above.

Mathematics

The solidus is used in the display of ratios and fractions as in constructing a fraction using superscript and subscript as in ¹²³⁄₄₅₆ , or on the same level as in 23∕50. It should be used instead of a slash, and is preferred whenever possible.

The solidus is found in many legacy Apple Macintosh character sets. It can be typed on a Macintosh computer by pressing option+shift+1. Systems capable of fine typography display this result as a true fraction with small numbers.

Unicode also distinguishes the Division Slash U+2215 ( ∕ ) which may be more oblique than the normal solidus character.

References

• Typography Words of the Day: Slashes, March 3, 2006.