Abnormal growth rings formed in response to leaning or crooked stems. In hardwoods it is termed "tension wood" and in softwoods "compression wood".
Reaction wood is wood formed in trees where the main stem is tipped from the vertical. It also often forms following the deflection of a lateral stem (branch) from its normal orientation. Reaction wood formed in hardwoods differs from that formed in softwoods. In softwoods, reaction wood is called compression wood; reaction wood in hardwoods is called tension wood. Both compression wood and tension wood are lower in quality than normal mature wood. As with juvenile wood, reaction wood is viewed as least desirable in lumber and in other products in which wood is used in solid form.
Distorted wood formed in leaning trunks and branches of trees. Reaction wood dries unpredictably, often twisting and cracking.