When should I use symbols?
Symbols are another form of shorthand and are particularly common in certain types of texts (e.g. mathematical, scientific or economic). By and large, they should be used sparingly in general texts that do not contain a lot of figures, particularly if they are not widespread or well known.
Be careful not to use symbols in running text with numbers written as words. Instead, use words with words and symbols with figures. Thus, write €7 million or seven million euros, but not € seven million. See the section on currency below for the UOC's preferences regarding references to monetary sums.