fundamental
Pronunciation: /fʌndəˈmɛnt(ə)l/
adjective
- forming a necessary base or core; of central importance: the protection of fundamental human rights interpretation of evidence is fundamental to the historian’s craft
- affecting or relating to the essential nature of something or the crucial point about an issue: the fundamental problem remains that of the housing shortage
- so basic as to be hard to alter, resolve, or overcome: the theories are based on a fundamental error
noun

Origin:
late Middle English: from French fondamental, or late Latin fundamentalis, from Latin fundamentum, from fundare 'to found'