The term 'Tree of Heaven' is a common name for two species of trees, Ailanthus (9 letters) and Ailantus (7 letters). Ailanthus is native to China and the Himalayas, while Ailantus is native to Japan and Taiwan. Both species are deciduous trees that can grow up to 30 meters tall and are known for their fragrant flowers and pinnate leaves. They are also considered invasive species in many parts of the world due to their rapid growth and ability to spread quickly.