chief constituent

foundation infrastructure source

authority backbone basis core essence essential evidence fundamental groundwork heart key origin principal principle root underpinning

important part primary element

auxiliary exterior exteriority outside surface trivia

annex branch top

aspect basis bottom line character core crux element lifeblood meaning nature principle quality reality root soul spirit structure substance

attribute backbone base being bottom burden caliber constitution entity essentiality fiber form fundamentals germ grain kernel life marrow meat nitty-gritty nub nucleus pith point property quiddity quintessence stuff timber vein

be-all and end-all essentia main idea name of game virtuality

abstract exterior exteriority outside top