In oak trees, the difference between early and late wood is related to the seasonal growth pattern of the tree.

Early wood, also known as springwood, is produced during the early part of the growing season when the tree has plenty of water and nutrients available. This wood is characterized by wider and lighter-colored rings with larger, thinner-walled cells. It is generally less dense and more porous than late wood.

Late wood, also known as summerwood, is produced later in the growing season when water and nutrients may be more limited. This wood is characterized by narrower and darker-colored rings with smaller, thicker-walled cells. It is generally more dense and less porous than early wood.

The contrast between early and late wood in oak is what gives oak its characteristic grain pattern, with the darker late wood forming the "veins" of the grain and the lighter early wood forming the "background" of the grain. This pattern is highly prized for its aesthetic appeal and is one of the reasons why oak is a popular choice for furniture, flooring, and other decorative woodwork.