In requesting or invoking Reiki words are not important. You can use the words your teachers have taught you or you can say it in your own words. More important than words is how you feel.
Feeling grateful and certain that the healing will take place and being ready to receive it is the best thing to do. Being grateful during opening, middle and closing a healing session is all it takes.
If you are religious, you can think of Reiki as the energy of God. If you are of a scientific bent of mind, you can think of Reiki as Pure Energy. An intelligent Energy that created this Universe.
One of my student calls Reiki as ‘Reiki Maa’. Reiki is an energy and Energy means Shakti in Sanskrit. And Shakti also refers to Goddess Shakti. So it is apt to address Reiki as Reiki Maa or Mother Reiki, he says.
It doesn’t matter how you address Reiki. It is ultimately the energy of the Universe. So you can have a scientific view of Reiki or a religious view of Reiki. It doesn’t matter. In both cases you can benefit.
If you have a certain view of Reiki, don’t criticize others who have a different view than you. Because all are valid point of views. Nobody knows the ultimate truth, unless they are enlightened.
When you are enlightened you can see things as they are. You are not coloured by what society teaches you.