Out of one, there becomes two, and so the '2'nd dimension is symbolized by the number '2'. As well, space is symbolized by the number '2', and by all even numbers, as space exists as the '2' to the '1' of time. Time and space are also known by other names. Time is known as 'energy', and space is known as 'mass' or 'matter'. Time is that which 'moves', and space is that which is 'still'.
Energy is motion, and motion is time.
Matter is stillness, and stillness is space. The Euclidean 'ray' well symbolizes the universe at this stage of evolution, as time gives rise to space, but space does not give rise to time. As space is '2', space is finite. As a finite amount of space can pass through a finite amount of time, in the '2'nd dimension time is also now finite. In the third dimension, there exists 'light'.