keystone
- 01 C1 Advanced
n.the middle stone at the top of an arch that holds all the other stones in place.
n.the central wedge-shaped stone at the summit of an arch, which locks the other stones into position and allows the structure to bear weight.
Simple“The builder carefully placed the keystone to finish the stone bridge.”
In context“Without the structural integrity provided by the keystone, the entire vaulted ceiling would have collapsed under its own weight during the restoration.”
Teacher's tipThis is the literal origin of the word; it is helpful to show students a diagram of an arch to explain the physical necessity of this stone.
- 02 C1 Advanced
n.the most important part of a plan, idea, or system that everything else depends on.
n.the central supporting element of a policy, system, or line of reasoning upon which all other parts depend.
Simple“Trust is the keystone of any healthy relationship.”
In context“The right to free speech is often described as the keystone of a democratic society, supporting all other individual liberties.”
Teacher's tipThis is the most common way students will encounter the word in academic reading or journalism.
Synonyms - 03 C2 Proficiency
v.to change the shape of a projected image because the projector is at an angle.
v.to distort a projected image into a trapezoidal shape by projecting it onto a surface at a non-perpendicular angle.
Simple“The image on the screen looked like a triangle because the projector was keystoning.”
In context“Modern digital projectors often include a feature to automatically correct keystoning when the device cannot be placed directly in front of the screen.”
UsageOften used in the context of 'keystone correction' in digital media.
Teacher's tipThis is a very specific technical use; most learners only need to recognize it in the context of audio-visual equipment.
“It is seen as a keystone achievement of US conservation efforts.”
“When combined with transplanting keystone epiphytic ferns, this could kick-start recovery of canopy ecosystems unique to RNSP.”
From key + stone. Definition 4 (retail) possibly originated in the jewelry industry in the magazine called "Jewelers' Circular-Keystone".
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.