dimensionless number

1. A number representing a property of a physical system, but not measured on a scale of physical units (as of time, mass, or distance). Drag coefficients and stress, for example, are measured as dimensionless numbers.

Example Sentences

The Deborah number is an example of a dimensionless number: Since we divide one time period by another, the ratio does not have any unit.

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The point of this laborious procedure is that this combination of multiplication and division produces a pure, dimensionless number.

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In physics there is a dimensionless number, the reciprocal of the fine structure constant, whose value to the best of our experimental knowledge is 137.035999679 with an uncertainty of 94 in the final two digits.

Read more on New York Times