Rounding: Rounding means making a number simpler but keeping its value close to what it was. 

Truncate: is shortening a number at a particular place value and filling in any zeros to keep it the same size. (Cut off)

Decimal places: are positions of the digits to the right of a decimal point.

Significant figure: A digit that gives meaning to a number. The most significant digit is the first non-zero number. 

Inequality: An inequality compares two values, showing if one is less than, greater than, or simple not equal to another value.   (Click HERE for a visual explanation of comparison symbols) 

Error intervals: are the limits of accuracy when a number has been rounded or truncated.