heart·wood 
(härtwd′)
(härtwd′)n.
The older, nonliving central wood of a tree or shrub, usually darker and harder than the younger sapwood. Also called duramen.
- nonsensicalness
- non sequitur
- nonsexist
- nonsignificance
- nonsignificant
- nonsignificantly
- nonsked
- nonskid
- nonslip
- non-small cell lung cancer
- nonsmoker
- nonsmoking
- nonspecific
- nonstandard
- nonstarter
- nonsteroid
- nonsteroidal
- nonstick
- nonstop
- nonstrange quark matter
- nonstress test
- nonsuch
- nonsuch
- nonsuit
- nonsupport