Modulus of elasticity is a measure of how much something stretches when a force is applied provided you don’t stress it beyond its elastic capacity. It often correlates with strength, but not always.

To calculate how much something will stretch under a force:

Extension = Force x Length / (E x Area)

Wood has a decent modules of elasticity for its weight, but it’s E is lot less than most building materials. Something like 2-8% that of steel depending of species.