The following are catagories with their defintions of a Hazard Tree and Defects.
- A standing tree, either live or dead, having defects, singly or combined, in roots, butt, bole, or limb, which predispose it to mechanical failure in whole, or in part, and which is so located that such failure has a probability of injury and damage to persons and property. --Peter Gaidula, California Dept. of Parks and Recreation.
- A tree hazard refers to any potential tree failure due to a structural defect that may result in property damage or personal injury.—"Tree Hazards: Recognition and Reduction in Recreation Sites," 1981.
- A tree can be considered potentially hazardous if it is situated in an area frequented by people or is located adjacent to valuable facilities and has defects in roots, stem or branches that may cause a failure resulting in property damage, personal injury or death.—Tree Hazards in Recreation Sites in British Columbia.
- Injury or disease that seriously weakens the stems, roots or branches of trees, predisposing them to fail
- Structural problems arising from poor tree architecture, including V-shaped crotches in stems and branches that lead to weak unions, shallow rooting habits, inherently brittle wood, etc.