Underlying (adjective) — الأساس الخفي: Fundamental; lying beneath the surface. Below are 7 words with a similar meaning; the linked ones have full GL Dictionary entries with their meaning in Arabic.
Forming an essential foundation — fundamental, elementary, or the simplest necessary level of something; also: a core principle or starting point
The part of a plant that grows underground; the origin or cause of something.
Existing but not yet developed or visible.
fundamentalessentialhiddenprimary
Below conscious awareness; mental activity we are not aware of.
Hidden, especially a hidden purpose.