fundamental
UK: ˌfʌndəˈment(ə)l | US: ˌfʌndəˈment(ə)l
adj. forming a necessary base or core; of central importance
n. (fundamentals) a basic principle or essential part
The word "fundamental" traces back to Latin fundamentum (foundation), derived from fundare (to lay the base), which itself comes from fundus (bottom, base). The morpheme "fund" preserves the core idea of a foundation, while "-ment" (Latin -mentum) forms nouns indicating results or means, and "-al" (Latin -alis) turns it into an adjective. Over time, "fundamental" evolved from literal foundations (e.g., buildings) to abstract bases (e.g., principles).
The fundamental rules of physics apply universally.
She lacks a fundamental understanding of the topic.
The course covers the fundamentals of programming.
Trust is fundamental to any healthy relationship.
Their argument ignored a fundamental flaw in the theory.