Heartwood (noun)

The older, harder, and darker central part of a tree trunk or branch, that is no longer active in water conduction and is more resistant to decay than the surrounding sapwood.

Origin:

The word heartwood comes from the combination of the words heart and wood, it refers to the central, older and harder part of a tree's trunk or branch.

Examples:

1. Heartwood is denser and more durable than sapwood.
2. The heartwood of this tree is dark brown in color.
3. Heartwood is not as easily worked as sapwood.
4. Heartwood is often used for making furniture or flooring.
5. The heartwood is resistant to decay and insects, making it ideal for use in construction.