GUI vs graphical user interface

GUI and graphical user interface both are nouns.

Word	Noun	Adjective	Verb	Adverb
GUI	Yes	No	No	No
graphical user interface	Yes	No	No	No

As nouns, GUI and graphical user interface are synonyms defined as:

GUI and graphical user interface: a user interface based on graphics (icons and pictures and menus) instead of text; uses a mouse as well as a keyboard as an input device

GUI (noun)	graphical user interface (noun)
a user interface based on graphics (icons and pictures and menus) instead of text; uses a mouse as well as a keyboard as an input device	a user interface based on graphics (icons and pictures and menus) instead of text; uses a mouse as well as a keyboard as an input device