The Japanese word for wood is
木

き - ki

Japanese Definition

木
1. n. a tree or shrub
2. n. wood, timber, lumber
3. n. (graph theory computer science) a tree (data structure)
4. n. (theater sumo, etc.) a clapper used to signal the opening or closing of a match or play
5. n. (ng-lite, Combining form of :) tree; wood
6. n. a tree
7. n. wood grain
8. n. a tree; more specifically, a living tree
9. n. the bent and gnarled trunk or roots of an old tree
10. n. wood, lumber
11. n. something made of wood
12. n. in ancient China, a wooden musical instrument
13. adj. (derogatory) wooden, as of a person's character or behavior
14. adj. (derogatory) wooden, as of a person's mental abilities: blockheaded, stupid, dimwitted

木材
1. n. timber - trees in a forest regarded as a source of wood.
2. n. material wood, (UK) timber, (US) lumber - wood that has been pre-cut and is ready for use in construction.