Section 8.7. Letterlike Symbols
8.7. Letterlike SymbolsThis block contains a large number of characters that are historically based on letters or letter combinations but might be shaped differently and, most important, are used in specialized meanings. For example, a symbol formed from the letter "R" by doubling its vertical line or all lines (ℝ) is conventionally used to denote the set of all real numbers in mathematics. Frequently used characters of this type include:
This block does not contain all Unicode characters that have originally been formed as stylized variants of letters. Some such characters belong to other blocks due to the history of character codes. Some characters in this block are redundant duplicates of normal letters but included into Unicode for compatibility. For example, although there is a character named "kelvin sign" in this block, it is not meant to be used instead of the normal letter "K" when expressing thermodynamic temperatures. The "kelvin sign" has been taken into Unicode only to allow existing data to be converted to Unicode so that a distinction between normal "K" and a kelvin sign is preserved, if it exists in the original data. Thus, contrary to what many people think after finding this block, many characters in it are not more appropriate than the corresponding normal letters. It is true that using "kelvin sign" for example would contain more semantic information, since the letter "K" as such has a large number of different uses and interpretations. However, it would not be feasible to disambiguate characters by using different codes for something that is essentially identifiable as a single character. We will return to this issue in the discussion of using letters in SI notations. |
(U+2116), used in some languages (with some glyph variation by language) to mean "number (e.g., "