keystone

[kee-stohn]

noun

1. the wedge-shaped piece at the summit of an arch, regarded as holding the other pieces in place.

2. something on which associated things depend.

   the keystone of one's philosophy.

   Synonyms: linchpin, foundation, principle, basis

3. Also called keystone sack. Baseball Slang.,  second base.

keystone

/ ˈkiːˌstəʊn /

noun

1. Also called: headstone.  quoin. the central stone at the top of an arch or the top stone of a dome or vault

2. something that is necessary to connect or support a number of other related things

Word History and Origins

Origin of keystone¹

First recorded in 1630–40; key ¹ + stone

Example Sentences

Despite the pile-up of particulars, Metcalfe knows he must find the lost poem, that it is the keystone without which the story crumbles into insignificance.

From Los Angeles Times

The orangutan is a keystone species and plays a vital role in maintaining the health of the ecosystem.

From Salon

Sunflower sea stars are considered a keystone species, meaning they are critical in regulating the stability and diversity of their ecosystems.

From Los Angeles Times

"This is a keystone appointment for us and an integral part of our five-year strategy as we look to achieve sustainable success for our senior men's side," said Tierney.

From BBC

"You targeted the police as a keystone of government power," he added.

From BBC

Related Words

• base 
• cornerstone 
• foundation 
• fundament