Final answer:
The number inside the brackets of an array definition is the size, while in an assignment statement, it is the index.
Step-by-step explanation:
The number inside the brackets of an array definition is the size of the array, indicating how many elements the array can hold. However, the number inside the array's brackets in an assignment statement, or any other statement that works with the contents of the array, is the index of the specific element being referenced or manipulated.
For example, int myArray[5]; defines an array named myArray with a size of 5, meaning it can contain 5 elements. When you see myArray[2] = 10;, it means we are assigning the value 10 to the element at index 2 of the myArray.