requirement or congenital
needed, necessary, required
Some synonyms for pivotal are: Crucial Middle Essential Focal Vital central cardinal axial critical principal
Synonyms for the word "imperative" are commanding, mandatory, essential, masterful.
vital, important, necessary, critical, crucial, key, indispensable
There are several listed synonyms for the word necessities. Some include cause, essential, demand, obligation, claim, imperative, and the word essence.
MTOCs. Essential and Ancient, they would be Micro Tubule Organizing Centers.
principal, first, leading, chief, main, central, key, essential
Some synonyms for Vital are-Essential,Necessary,Crucial, etc.
The word requisite means a thing that is necessary for the achievement of a specific end. Some synonyms for requisite are; essential, must, requirement, needful or indispensable.
The verb form has the synonyms asked, needed, requested, ordered, mandated or called for. The adjective form has the synonyms necessary, needed, essential, vital, requisite, prerequisite, or mandatory.
Yolk also means (besides a part of an egg) "the essential part, the inner core". So "center" or "core" are synonyms.
They are synonyms.