core
n. countable B2 Upper Intermediate Oxford US //ˈkɔɹ// UK //kˈɔː// core
n. the central or most important part of something. It can be the hard middle of a fruit or the main idea of a plan.
n. the central, innermost, or most essential part of an object or concept. Often used to describe the foundational principles of a system or the physical center of a planetary body.
The core of the apple contains the seeds.
The government's new policy has environmental protection at its core, influencing every decision they make.
Engineers must ensure the reactor core remains stable under extreme pressure to prevent a catastrophic failure of the entire power plant system.
Usage
Often used in the phrase 'at the core of' to identify a primary cause or central theme.