Fundamental
Fundamental adjective - Of or relating to the simplest facts or theories of a subject.
Usage example: the purpose of the course is to furnish students with fundamental knowledge of human reproduction
Key is a synonym for fundamental in property topic. In some cases you can use "Key" instead the word "Fundamental" as an adjective or a noun, when it comes to topics like principal, essential, basic, central. popular alternative
Key
Key adjective - Of the greatest possible importance.
Usage example: first—and this is key—I wasn't even there that evening
Fundamental is a synonym for key in essential topic. You can use "Fundamental" instead the word "Key" as an adjective or a noun, if it concerns topics such as property, crucial. popular alternative
Mutual synonyms
Related pairs
Both words in one sentence
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If you manage to make a truly critical change at a key point in time you can create fundamental changes the world, such as the noted ability to jump between the α from the β lines, but it's still fundamentally one single timeline.
Source: Visual Novel / Steins;Gate -
In All Your Base Are Belong To Her, Buffy alumni Dawn arrives in the universe inhabited by SG:1, and quickly discovers that being the Key allows her to interface with the Stargate network on a fundamental level.
Source: How Do I Shot Web? -
He describes the trope as the fundamental key to all other animation- once you can animate a clean walk, anything else becomes easy.
Cite this Source
Key and Fundamental. (2016). Retrieved 2026, July 21, from https://thesaurus.plus/related/fundamental/key
Fundamental & Key. N.p., 2016. Web. 21 Jul. 2026. <https://thesaurus.plus/related/fundamental/key>.
Key or Fundamental. 2016. Accessed July 21, 2026. https://thesaurus.plus/related/fundamental/key.
Google Ngram Viewer shows how "fundamental" and "key" have occurred on timeline