The stiffness of lumber is denoted by which letter?

• A. A
• B. E
• C. G
• D. K

Answer: (B)

Stiffness is quantified by the material’s modulus of elasticity, known as Young’s modulus, and it is denoted by the letter E. In lumber, E measures how much the wood elastically deforms along the grain under load; a higher E means the wood is stiffer and deflects less under the same force. This relationship is why beam deflection formulas include E in the denominator—stiffer wood resists bending more. The letter G, by contrast, refers to the shear modulus, which governs resistance to shear rather than bending stiffness. The other symbols aren’t standard for representing stiffness in lumber. So the symbol you look for when talking about stiffness is E.