touchstone

standard, criterion, gauge, yardstick, touchstone mean a means of determining what a thing should be. standard applies to any definite rule, principle, or measure established by authority.

• • standards of behavior

criterion may apply to anything used as a test of quality whether formulated as a rule or principle or not.

• • questioned the critic's criteria for excellence

gauge applies to a means of testing a particular dimension (such as thickness, depth, diameter) or figuratively a particular quality or aspect.

• • polls as a gauge of voter dissatisfaction

yardstick is an informal substitute for criterion that suggests quantity more often than quality.

• • housing construction as a yardstick of economic growth

touchstone suggests a simple test of the authenticity or value of something intangible.

• • fine service is one touchstone of a first-class restaurant