Quote:The notation to state a resistor's value in a circuit diagram varies. The European notation BS 1852 avoids using a decimal separator, and replaces the decimal separator with the SI prefix symbol for the particular value. For example, 8k2 in a circuit diagram indicates a resistor value of 8.2 kΩ. Additional zeros imply tighter tolerance, for example 15M0. When the value can be expressed without the need for an SI prefix, an "R" is used instead of the decimal separator. For example, 1R2 indicates 1.2 Ω, and 18R indicates 18 Ω. The use of a SI prefix symbol or the letter "R" circumvents the problem that decimal separators tend to "disappear" when photocopying a printed circuit diagram.

Quote:The usage of the Latin letter E instead of R is not standardized in IEC 60062, but nevertheless sometimes seen in practice. It stems from the fact, that R is used in symbolic names for resistors as well, and it is also used in a similar fashion but with incompatible meaning in other part marking codes. It may therefore cause confusion in some contexts. Visually, the letter E loosely resembles a small Greek letter omega (ω) turned sideways. Historically (f.e. in pre-WWII documents), before ohms were denoted using the uppercase Greek omega (Ω), a small omega (ω) was sometimes used for this purpose as well, as in 56ω for 56 Ω. However, the letter E is conflictive with the similar looking but incompatible E notation in engineering, and it may therefore cause considerable confusion as well.