“The fast food market in the U.S. is highly competitive.”

You are writing a report about a company. This company sells products that a lot of other companies also sell. You are introducing the company. You write:

The fast food market in the U.S. is highly competitive.

the (something) market

A "market" is a large group of people that you are able to sell something to. Companies usually try to focus on a specific "market" that belongs in a certain geographical area and includes people of a certain age, gender, and income.

You can discuss a certain market by using the expression "the ___ market". Some examples are:

• the stock market
• the automotive market (cars)
• the fiction publishing market (printing novels)

highly competitive

A market, a sports league, a competition, etc. is "competitive" when several people or groups are trying hard to win against each other.

When something is very competitive, you describe it as "highly competitive".

a competitive market

The word "competitive" is often used to describe a "market".