i a+bi x+i*y
As the basic imaginary unit sqrt(-1), i is used to enter complex numbers. You can also use the character j as the imaginary unit. If you want to create a complex number without using i and j, you can use the complex function.
Since i is a function, it can be overridden and used as a variable. However, it is best to avoid using i and j for variable names if you intend to use them in complex arithmetic.
If desired, you can use the character i without a multiplication sign as a suffix in forming a complex numerical constant.
For speed and improved robustness, you can replace complex i and j by 1i. For example, instead of using
a = i;
a = 1i;