Word Study
heartwood
CIDE DICTIONARY
heartwood, n.
The hard, central part of the trunk of a tree, consisting of the old and matured wood, and usually differing in color from the outer layers. It is technically known as duramen , and distinguished from the softer sapwood or alburnum . [1913 Webster]
OXFORD DICTIONARY
heartwood, n. the dense inner part of a tree-trunk yielding the hardest timber.
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