The phrase "an important segment" is correct and usable in written English.
You can use it when referring to a significant part or portion of a whole, often in contexts like business, research, or demographics.
Example: "The youth market is an important segment of our target audience that we need to focus on."
Alternatives: "a crucial part" or "a key component".
"This is an important segment of the economy here," said Mr. Keegan.
It was a period when our children completed an important segment in their Jewish experience.
The results do not include on-demand viewings, typically an important segment for HBO.
Given that fierce debate, signs of recovery in an important segment of the mortgage-backed bond market are worth watching.
This is the season when stores sell millions of garden plants, which are an important segment of the business.
It was then that Iran fractured, causing an important segment of the ruling elite to revisit the country's most fundamental national decision.
The islands form an important segment of the Antilles (West Indies) island chain, which continues east and then south in a great arc enclosing the Caribbean Sea.
Although the straw poll, like others, carries no scientific weight, the results are scrutinized for clues to the thinking of conservative Christians, an important segment of Republican voters.
The first is a deep frustration that is shared by an important segment of the population and that has been festering for a considerable period of time.
But Mr. McCain's statements today, following his attack on the leaders of the Christian right on Monday, seemed to continue if not escalate his effort to marginalize what has been an important segment of the Republican Party for two decades.
"The literacy field has been a little slow to realize what an important segment of the population being served in adult education are non-native speakers," Ms. Reddy said.
