gross sales vs income

gross sales and income both are nouns.

Word	Noun	Adjective	Verb	Adverb
gross sales	Yes	No	No	No
income	Yes	No	No	No

As nouns, income is a hypernym of gross sales; that is, income is a word with a broader meaning than gross sales:

gross sales: income (at invoice values) received for goods and services over some given period of time
income: the financial gain (earned or unearned) accruing over a given period of time

gross sales (noun)	income (noun)
income (at invoice values) received for goods and services over some given period of time	the financial gain (earned or unearned) accruing over a given period of time