Timber! That's the call of warning you hear before a tree falls. That's because those lumberjacks are going to use the tree to make timber, otherwise known as "lumber" or the wood used for construction.
Timber can actually be the trees used to make or build something, or the wood that comes from those trees, which you could also call "lumber." You might think that when a pirate yells "shiver me timbers!" he's referring to his wooden peg leg. But the timbers he's talking about are actually the boards and planks used to build the frame of a ship.