A shrub or bush, on the other hand, is a woody plant having multiple stems growing from the same roots and is usually lower growing. An oak is a tree. Most lilacs are shrubs. At the other end, trees can be gigantic. Some species, like Giant Sequoias, Coast Redwoods, Douglasfirs, and some Eucalyptus, grow 300 feet tall or more and have trunks 30 feet across.
Some species also have very long life spans.
The Great Basin Bristlecone Pine often lives longer than 4,000 years. That's right, four thousand. Some trees living today are as old as the most ancient pyramids of Egypt. They were living when civilization began in the Indus Valley and the earliest dynasties of China were founded. These trees were unimaginably ancient when Troy fell to the Greek invaders.