Reiki is written in two Japanese kanji or characters, Spiritual (&) Energy
The word 'Reiki' is used in the West to denote a healing system.
The founder of our Modern Reiki System, Mikao Usui didn't use this term, his teachings were more commonly called 'Usui Do' (the Way of Usui) and the healings 'Usui teate' or Usui's form of hands-on healing. Later, the word Reiki was added or substituted, to signify the system utilized spiritual energy.
In Chinese, the same two kanji are used for 'Ling Chi'
"Ling Chi is the subtylest and most highly refined of all the energies in the human system and the product of the most advanced stage of a practice, whereby the ordinary energy of the body are transformed into pure spiritual vitality. This type of highly refined energy enhances spiritual awareness, improves all cerebral functions, and constitutes the basic fuel for the highest level of spiritual work." (Ling Gung: Harnessing the Power of the Universe - Daniel Reid)
Just for today, use the kanji as a meditative focus, 'sit with it.'