What is another word for keystone sack?
Pronunciation: [kˈiːstə͡ʊn sˈak] (IPA) 
The term "keystone sack" can refer to a number of synonyms, including "cornerstone," "linchpin," and "critical element." Each of these terms suggests a central importance or essential nature, with the keystone sack being the foundation upon which something else depends. Similarly, "key component," "vital piece," and "essential element" all convey the idea of an important building block without which the overall structure would collapse. Other potential synonyms might include "lynchpin," "pivot point," or "mainstay," all of which suggest the same kind of foundational role in some context or other. Whatever term is used, the idea remains the same: a vital, irreplaceable element that cannot be neglected or removed without serious consequences.
