referential (content)
This refers to a device that allows people to read texts electronically.

metalingual (code)
This can be used in a way that people get texts remotely and read texts electronically.

formal (form)
This consists of electronic texts, screen, keyboard and page tuners.

expressive (addresser)
The addressers are the authors of books who allow Amazon to deliver their books via this device.

phatic (contact)
The addressers and the addresses can be contacted only via this device. Thus, addressers, who do not allow Amazon to deliver their books, and addressees, who do not have this device, will be excluded.  

conative (addressee)
The addressees are readers who have this device.

contextual (situation)
In the situation where people want to read texts electronically while they are traveling or studying