Final answer:
The operator used to create arrays at runtime is the 'new' operator, which initializes the array with a specified size.
Step-by-step explanation:
The operator used to create arrays at runtime in many programming languages like Java and C# is the new operator. When you want to create an array dynamically, that is, at the time the program is running, you use the new operator followed by the type of elements you want the array to hold, and specify the number of elements or the size of the array in square brackets. For example, in Java, to create an integer array with 10 elements, you would write int[] array = new int[10];.