Example: dating the tree rings of a beam from a ruin in the American Southwest to determine when it was built.
The science that uses tree rings to study present climate and reconstruct past climate.
Dendrochronology is the formal term for tree-ring dating, the science that uses the growth rings of trees as a detailed record of climatic change in a region, as well as a way to approximate the date of construction for wooden objects of many types.
As archaeological dating techniques go, dendrochronology is extremely precise: if the growth rings in a wooden object are preserved and can be tied into an existing chronology, researchers can determine the precise calendar year--and often season--the tree was cut down to make it.
But for the specimen to be useful in extending the tree-ring chronology, the absolute calendar age of its rings must be determined.