January 1994
Symbols for mathematical quantities that are used in equations normally consist of one full-size letter, possibly accompanied by indices or labels as superscripts or subscripts, or within parentheses. Abbreviations of two or more letters should not be used as symbols in mathematical expressions, with a few well-established exceptions such as the trigonometric functions, standard dimensionless parameters [e.g., Re (Reynolds number), Pr (Prandtl number)], c.c., H.a., and H.c.
Abbreviations such as RRR for residual resistance ratio or Int for interaction term may be used in the text, but if they enter into mathematical expressions they are almost as awkward as full words and in some cases may be mistaken for a product of single-letter symbols. They should be replaced with conventional symbols such as rR and Hint . In particular, multiletter terms used in the language of computer programming, such as SQRT, should be converted.
Examples of conversions to single-letter symbols:
| Description | Multiletter symbol |
Single-letter symbol |
|---|---|---|
| Ionization potential | IP | Vion, Vi |
| Volume | Vol | V, ${\cal {V}}$ |
| Kinetic energy | KE | Ekin, Ek |
| Potential energy | PE | V, Vpot |
| Electron affinity | EA | Ae |
| Isomer shift | IS | δIS, δ(IS) |
| Quadrupole splitting | QS | ΔQS, Δ(QS) |
| Differential cross section | DCS | dσ/dE |
| Branching ratio | BR | B |