10 + 5 = 15. Here we are using the = sign which indicates a balance of both sides.

However, there could also be number sentences which say:

12 + 6 = 9 is not true, but 12 + 6 = 18 is true.

Therefore, a number sentence does not necessarily have to be true. However, every number sentence gives us information, and based on the information provided; it is possible to change the statement from false to true.

So, a number sentence contains numbers, mathematical operations, equal to or inequality sign and a number after the equality or inequality sign. If we remove any of these components, it will no longer be a number sentence.