Nearest thousandth : Rounding to the nearest thousandth refers to rounding such that the resulting number is a multiple of one thousandth. If the ten thousandths digit is 5 or more the thousandths digit is rounded up, otherwise it is rounded down.

Number : A number $x$ is a mathematical symbol representing a quantity.

Round : Round can be a property of a shape, meaning that it does not have any corners. For example a circle can be described as round. A number can be informally described as round if it does end in one or several zeros such that rounding that number to a certain number of digits does not change the number.

Rounding : Rounding is the operation of changing a number to a number that is close to the original number. Rounded numbers are often used to do quick rough calculations for estimation purposes. For example rounding $4549$ to the nearest thousand results in 5000, rounding the same number to the nearest hundred results in 4500. In general one rounds up if the digit after the digit we try to round to is 5 or more, otherwise one rounds down.

Ten : Ten refers to the number $10.$

Thousandths digit : The thousandths digit is the third digit after the decimal point. It counts multiples of $\frac{1}{1,000}.$

Absolute value : The absolute value $|x|$ of a number $x$ is defined as the value of $x$ ignoring any potential minus sign. For example $|-2|=2$ and $|2|=2.$ In other words $|x|=x$ for $x\geq 0$ and $|x|=-x$ for $x\lt 0.$

Addition : Addition is the mathematical operation that describes increasing a number by an amount equal to a second number. The mathematical symbol for addition is the plus sign $+.$ The term addition is also used for a generalization of this basic operation on numbers to functions, vectors and matrices.

Negative : A number is negative if it is $\lt 0.$

Number : A number $x$ is a mathematical symbol representing a quantity.

Sum : A sum is the result of an addition.

Degree : For angles one degree is defined as the angle represented by a $\frac{1}{360}$ of the angle represented by a full circle. For measuring temperatures one can use either degrees Celsius or degrees Fahrenheit. In a polynomial the degree describes the highest exponent of $x$ that has a non-zero coefficient. For example the degree of $1+x+x^2$ is 2.

Degrees Celsius : The Celsius scale for measuring temperature is specified by saying that $0^{\circ}$ C is the temperature at which water freezes and $100^{\circ}$ C is the temperature at which water boils. To convert degrees Fahrenheit into degrees Celsius one can use the formula $C=\frac{5}{9}\cdot(F-32).$

Degrees Fahrenheit : The Fahrenheit scale for measuring temperature is specified by saying that $32^{\circ}$ F is the temperature at which water freezes and $212^{\circ}$ F is the temperature at which water boils. To convert degrees Fahrenheit into degrees Celsius one can use the formula $C=\frac{5}{9}\cdot(F-32).$