WOOD' (4 letters) The term 'TREE LIQUID' can be broken down into two crossword solutions: SAP (3 letters) and WOOD (4 letters). SAP is a type of tree liquid that is produced by plants, and is composed of water and nutrients. It is used to transport nutrients and water throughout the plant, and is also used in the production of maple syrup. WOOD is a type of tree liquid that is produced by trees, and is composed of cellulose and lignin. It is used to make furniture, paper, and other products.