Typefaces Roman type

SI units and their symbols have distinctive type styles. Items given in italic type are variables, quantity symbols, superscripts and subscripts if they represent variables, quantities, or running numbers. Items given in roman type are unit symbols, superscripts, and subscripts that are descriptive. The typeface used in the surrounding text of the document does not change these rules. 

Names of restriction endonucleases should follow the typeface conventions of the names from which they were derived use italic type for the three-letter portion derived from the genus and species name use roman type for additional strain designators (letters and/or arabic numerals) and for the roman numeral identifiers. 

Type weight, definition and examples, 287 Typefaces, See Boldface type, Italic type, Roman type... 

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