A number sentence is an equation or inequality written using numerals, and operations.
Number sentences can be written using fractions, decimals, negative
numbers, real numbers, a combination of these, and so forth...
Examples of number sentences using whole numbers only
Addition sentence : 4 + 2 = 6
Subtraction sentence : 16 - 7 = 9
Multiplication sentence : 6 × 8 = 48
Division sentence: 12 ÷ 4 = 3
Examples of number sentences using fractions only
Addition sentence : 1/4 + 3/4 = 1
Subtraction sentence : 1/2 - 1/4 = 1/4
Multiplication sentence : 2/5 × 1/3 = 2/15
Division sentence: 5/4 ÷ 5/4 = 1
In elementary schools, when students have not been exposed just yet to the concept of "equation", the expression "number sentence" is used and it is easier for students to understand.