Answer:
Debt is money owed, and the deficit is net money taken in (if negative). Debt and deficit are two of the most common terms in all of macro-finance, and they're also one of the most politically relevant, inspiring legislation and executive decisions that affect many people.
Despite starting with a common syllable and having deceptively similar meanings, the words don’t even have the same etymology. “Debt” derives from the Latin for “owe,” while “deficit” comes from the word for “lacking,” or “fail”—literally, the opposite of “to do.”