middle, heart, focus, core, nucleus, hub, pivot, kernel, focus
Synonyms for the word library include; athenaeum, atheneum, bibliotheca, book collection, book room, information center, media center, reference center, and study.
The word is center.
Omphalos, but I don't think it has a standard adjectival form.
Yolk also means (besides a part of an egg) "the essential part, the inner core". So "center" or "core" are synonyms.
They are synonyms.
Synonyms
Relative and kin are synonyms.
They are synonyms.
synonyms
The synonyms for upon is on
synonyms for prominence:importancefamestatureprestige
Are there synonyms for washable