"core" is a correct and usable word in written English. You can use it to refer to the most important or essential part of something, such as an idea, argument, or system, or as a noun meaning the central or innermost part of something. For example: "The core principles of the company's values are integrity, respect, and innovation.".
"We lose core user after core user by not addressing simple trolling issues that they face every day".
But our core voters turned out.
"It is a good deal, a deal that meets our core objectives … If this framework leads to a final, comprehensive deal, it will make our country, our allies and our world safer".
The legal argument focused on the challenge to core of the legislation – its requirement that almost all Americans buy health insurance.
Levitt argued that a focus on products rather than on customers led the companies to misunderstand their core business.
Whether or not the EPA's own surveys can be trusted, the move by Republicans to denounce water regulation and pitch it as the enemy of the foundational American ideal of private property might not be a slam-dunk for the American right – even among their core supporters.
Other so-called "core cities" now began to organise.
I love the desktop app, it’s always running on my Mac. Ludwig is the best English buddy, it answers my 100 queries per day and stays cool.
Cristina Valenza
Retail Lead Linguist @ Apple Inc.