Something is said to be constant when it does not change. The color of a bus could be red, blue, green, or any other color, and this can change over time if it is repainted. So the color of a bus is not constant. The value 5, however, is constant. And so is a triangle. 5 will always be 5, in the same way a triangle will always be a triangle. Constants in programming, therefore, represent quantities that cannot change throughout the duration of a program.