business vs sector

business and sector both are nouns.

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

As nouns, sector is a hypernym of business; that is, sector is a word with a broader meaning than business:

business (noun)	sector (noun)
the principal activity in your life that you do to earn money	measuring instrument consisting of two graduated arms hinged at one end
the activity of providing goods and services involving financial and commercial and industrial aspects	a particular aspect of life or activity
the volume of commercial activity	a social group that forms part of the society or the economy
incidental activity performed by an actor for dramatic effect	a portion of a military position
an immediate objective	the minimum track length that can be assigned to store information; unless otherwise specified a sector of data consists of 512 bytes
a rightful concern or responsibility	a plane figure bounded by two radii and the included arc of a circle
a commercial or industrial enterprise and the people who constitute it
customers collectively
business concerns collectively