The Shikai (始解, "Initial Release") is the second form (or first "upgraded" form) available to a Zanpakutō. To activate it, the Shinigami needs to learn the name of their Zanpakutō. This is not as easy as simply picking a name, as the living spirit of the Zanpakutō already has its own name. Therefore, the Shinigami must be able to communicate and harmonize with their Zanpakutō effectively, which requires being able to speak to the spirit within its world. A Zanpakutō can change size and shape depending on the spiritual strength of the owner.