Using symbols as abbreviations

Except for negative numbers (–23) and tolerances (±5 mm), in formal writing, do not use symbols as abbreviations—always spell out the term, such as “greater than $20 million”. Other common abbreviations are and/or, ~20m, @15%, and terms & conditions. It can, however, be helpful to set off numerical terms prefixed by <, >, ≤, and ≥ after the spelled-out term—for example “greater than or equal to 100 Mpa (≥100 MPa)”.

When a symbol is used as a prefixed abbreviation with a number, do not separate the number and symbol with a space. However, symbols are always spaced in equations (see Equations). Symbols commonly used as abbreviations are listed in various the topics under Standard abbreviations. For a complete list of symbols and their meanings, see Special characters.