be suitable; in others it may be impractical. In the previous example, 0.5 mm, 0.50 mm, or 0.500 mm would have been used to show uncertainty and significant figures. It is also common to state the precision explicitly, such as "" Another example: when the speed of light (exactly by the definition of the meter) is expressed as or then it is clear that it is between and , but when using , or , , or the unusual but short , this is not clear. A possibility is using or . On the other hand, engineering notation allows the numbers to explicitly match their corresponding SI prefixes, which facilitates reading and oral communication. For example, can be read as "twelve-point-five nanometers" (10−9 being nano) and written as 12.5 nm, while its scientific notation equivalent would likely be read out as "one-point-two-five times ten-to-the-negative-eight meters". Engineering notation, like scientific notation generally, can use the E notation, such that can be written as 3.0E−9 or 3.0e−9. The E (or e) should not be confused with the exponential e which holds a completely different significance. {| class="wikitable" style="padding:0; text-align:center; width:0" ! colspan="5" | SI prefixes |- !style="text-align:center" colspan="2" | Prefix !style="text-align:center" colspan="3" | Representations |- ! style="text-align:center" | Name ! style="text-align:center" | Symbol ! style="text-align:center" | Base 1000 ! style="text-align:center" | Base 10 ! style="text-align:center" | Value |- | quetta | Q | style="text-align:left;" | 100010 | style="text-align:left;" | 1030 | style="text-align:right;" | |- | ronna | R | style="text-align:left;" | 10009 | style="text-align:left;" | 1027 | style="text-align:right;" | |- | yotta | Y | style="text-align:left;" | 10008 | style="text-align:left;" | 1024 | style="text-align:right;" | |- | zetta | Z | style="text-align:left;" | 10007 | style="text-align:left;" | 1021 | style="text-align:right;" | |- | exa | E | style="text-align:left;" | 10006 | style="text-align:left;" | 1018 | style="text-align:right;" | |- | peta | P | style="text-align:left;" | 10005 | style="text-align:left;" | 1015 | style="text-align:right;" | |- | tera | T | style="text-align:left;" | 10004 | style="text-align:left;" | 1012 | style="text-align:right;" | |- | giga | G | style="text-align:left;" | 10003 | style="text-align:left;" | 109 | style="text-align:right;" | |- | mega | M | style="text-align:left;" | 10002 | style="text-align:left;" | 106 | style="text-align:right;" | |- | kilo | k | style="text-align:left;" | 10001 | style="text-align:left;" | 103 | style="text-align:right;" | |- style="background-color:#EEE" | colspan="2" | | style="text-align:left;" | 10000 | style="text-align:left;" | 100 | style="text-align:center;"