जो आवश्यक हो।

हमारा शरीर पाँच मुख्य तत्वों से बना है।
प्रधान, प्रमुख, मुख्य, मूल

Serving as an essential component.

A cardinal rule.
The central cause of the problem.
An example that was fundamental to the argument.
Computers are fundamental to modern industrial structure.
cardinal, central, fundamental, key, primal