This is the 468th most frequent Italian word.
economica
In Italian, "economica" means "cheap" or "affordable" in English.
In this sentence, 'economica' functions as an adjective that describes an object (the car) as being cost-effective or fuel-efficient.
Questa macchina è molto economica.
This car is very economical.
Here, 'economica' indicates that the dinner was affordable, referring to cost.
La cena al ristorante è stata economica.
The dinner at the restaurant was inexpensive.
This usage of 'economica' describes a proposed solution as non cost-effective or resource-efficient.