Lumber defects, which can affect both the appearance and structural integrity of wood, include a variety of growth and manufacturing flaws. Growth defects such as knots and knotholes occur where branches were once attached to the tree trunk, with knotholes forming when these knots fall out. Other natural defects include decay and insect damage, which compromise the wood's strength and durability.

Shakes are minor fractures that run along or across the wood's annual rings, while wane is characterized by missing wood or the presence of bark along a board's edge, typically resulting from the way the lumber is cut. Checks are radial cracks within the wood, appearing as the wood dries and shrinks circumferentially during the seasoning process.

Warping is a deviation from the wood's flat surface and can manifest as crooking, bowing, twisting, or cupping, each affecting the lumber's usability. Honeycombing refers to internal cracks caused by improper seasoning, which can weaken the wood internally.

Torn grain is another defect that occurs during the cutting or planing process, where the wood chips away, leading to a rough surface. Lastly, surface stains such as brown, green, or blue discolorations may develop after processing. These stains generally affect only the wood's appearance and not its strength.

Understanding these defects is crucial for managing wood quality and ensuring that lumber meets the necessary standards for construction and manufacturing uses.