heartwood
/ˈhɑrtˌwʊd/
noun
- The hard, dark, non-living central part of a tree trunk, surrounded by sapwood.
- The heartwood of an oak tree is much denser and more resistant to decay than the outer layers.
- As the tree aged, its heartwood grew darker and richer in color.
- Carpenters prefer using heartwood for furniture because it is stronger and less likely to warp.
Antonyms