why do we use engineering notation instead of scientific notation
Scientific notation Engineering notation (often named "ENG" display mode on scientific calculators) differs from normalized scientific notation in that the exponent n is restricted to multiples of 3. Consequently, the absolute value of m is in the range 1 ≤ |m| < 1000, rather than 1 ≤ |m| < 10. Though similar in concept, engineering notation is rarely called scientific notation. Engineering notation allows the numbers to explicitly match their corresponding SI prefixes, which facilitates reading and oral communication. For example, 6992125000000000000♠12.5×10−9 m can be read as "twelve-point-five nanometers" and written as 6992125000000000000♠12.5 nm, while its scientific notation equivalent 6992125000000000000♠1.25×10−8 m would likely be read out as "one-point-two-five times ten-to-the-negative-eight meters".
Bracket (mathematics) Historically, other notations, such as the vinculum, were similarly used for grouping; in present-day use, these notations all have specific meanings. The earliest use of brackets to indicate aggregation (i.e. grouping) was suggested in 1608 by Christopher Clavius and in 1629 by Albert Girard.[1]