If you’re doing any kind of scientific computing or electronics computations, “i” or “j” mean the imaginary number sqrt(-1). Some software, such as Matlab, hav

If you’re doing any kind of scientific computing or electronics computations, “i” or “j” mean the imaginary number sqrt(-1). Some software, such as Matlab, have those letters reserved for the common case of imaginary roots of a polynomial, and “ii” and “jj” as variables is a common coding convention. Whether “i” or “j” is your letter for imaginary numbers depends on if you’re an electrical engineer or not.