How can deflection be best defined?

Deflection is best defined as the degree to which a structural element is displaced from its original position under load. When discussing deflection, sag refers specifically to the downward displacement commonly observed in beams or other structural members when they are subjected to weight. This downward bowing can occur due to the bending of the material as it bears the load, manifesting as a sagging appearance.

In structural engineering, sagging is an essential consideration as it affects both the performance and safety of the structure. Excessive deflection can indicate that a beam is not performing adequately and may lead to structural failure if not properly addressed. Understanding deflection in terms of sag is crucial for carpenters and builders as it directly impacts design choices and load-bearing calculations when constructing buildings and other structures.