* Cellulose: This is the most abundant organic compound on Earth and makes up about 40-50% of wood. It is a complex carbohydrate that provides strength and rigidity to the wood.

* Lignin: This is a complex polymer that acts as a glue, binding the cellulose fibers together and giving wood its strength and water resistance. It makes up about 20-30% of wood.

While these are the most prominent substances, wood also contains smaller amounts of other compounds, such as:

* Hemicellulose: Another type of carbohydrate that adds to wood's structural integrity.

* Extractives: These are substances like resins, oils, and tannins that can contribute to wood's color, scent, and resistance to decay.

* Water: Wood can contain a significant amount of water, especially when freshly cut.