business vs biz

business and biz both are nouns.

Word	Noun	Adjective	Verb	Adverb
business	Yes	No	No	No
biz	Yes	No	No	No

As nouns, biz is a hyponym of business; that is, biz is a word with a more specific, narrower meaning than business:

business (noun)	biz (noun)
the principal activity in your life that you do to earn money	your occupation or line of work
the activity of providing goods and services involving financial and commercial and industrial aspects
the volume of commercial activity
incidental activity performed by an actor for dramatic effect
an immediate objective
a rightful concern or responsibility
a commercial or industrial enterprise and the people who constitute it
customers collectively
business concerns collectively