Tenacity

The quality or property of being tenacious.

• 1. Cohesiveness, toughness; viscosity, clamminess (of a liquid); also, adhesive quality, stickiness.
• 2. The quality of retaining what is held, physically or mentally; firmness of hold or attachment; firmness of purpose, persistence, obstinacy.

b. Retentiveness (of memory).

• 3. Tendency to keep fast hold of money; miserliness, niggardliness, parsimony. Obs.

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Tenacity is the customary measure of strength of a fiber or yarn. In the U.S. it is usually defined as the ultimate (breaking) strength of the fiber (in gram-force units) divided by the denier.

Because denier is a measure of the linear density, the tenacity works out to be not a measure of force per unit area, but rather a quasi-dimensionless measure analogous to specific strength.