For a long time, spoken words were used in computations. Then came numbers, process symbols and general numbers. Now you use such symbols as:
| symbol | you say | symbol | you say |
a  b |
a is larger than or equal to b | a  b |
a not equal to b |
a  b |
a is smaller than or equal to b | a  b |
a nearly equal to b |
| a < x < b | x larger than a and smaller than b | a  b |
a tends to b |
If a quantity is measured, it will not always be exact; for example, when you measure a length of 14 m, the digit 4 may be uncertain. An answer in the form 14 m or 0.014 km or 1400 cm does not affect its accuracy. It is determined by the number of valid digits. Here you have the two valid digits 1 and 4.