operating budget vs operating expense

operating budget and operating expense both are nouns.

Word	Noun	Adjective	Verb	Adverb
operating budget	Yes	No	No	No
operating expense	Yes	No	No	No

operating budget (noun)	operating expense (noun)
a budget for current expenses as distinct from financial transactions or permanent improvements	the expense of maintaining property (e.g., paying property taxes and utilities and insurance); it does not include depreciation or the cost of financing or income taxes