There are two main explanations for this problem. For example, a bag of four apples plus one apple is five apples, but a bag of four apples plus one apple is still a bag.

Addition is one of the four basic operations, which refers to the calculation of combining two or more numbers and quantities into one number and quantity. The symbol of addition is the plus sign "+". Connect items with a plus sign when adding.

First, the definition of addition:

Addition has been used to establish countless physical processes. Even in the simple case of adding natural numbers, there are many possible explanations and more intuitive expressions.

Second, perhaps the most basic explanation of addition lies in combination:

1. When two or more disjoint sets are merged into one set, the number of objects in the set is the sum of the number of objects in the original set.

This explanation is easy to imagine. It is also suitable for advanced mathematics; For a strict definition of its excitation, see the following natural numbers.

3. One possible solution is to consider a group of easily divisible objects, such as pies. Rods can not only form a set of rods, but also connect rods together, which explains another concept of addition: not adding rods, but adding the lengths of rods.