* Noun: This is the most common use. It refers to the system of production, distribution, and consumption of goods and services within a country or region.
* Example: "The global economy is experiencing a downturn."
* Adjective: This means "relating to or concerned with the economy."
* Example: "This is an economy-sized box of cereal."
* Verb: This is less common and means "to manage or use resources carefully."
* Example: "We need to economy our time and energy."
So, to determine the part of speech, you need to look at how it's used in a sentence.