dendrochronology

thumb|The growth rings of a tree at Bristol Zoo, [[England. Each ring represents one year; the outside rings, near the bark, are the youngest]] thumb|A "tree cookie" cross-section of a Pseudotsuga menziesii var. menziesii|Coast Douglas-fir tree displayed in the [[Royal Ontario Museum. The tree was over 500 years old when it was cut down in British Columbia in the 1890s. The markings indicating historical events were added in the 1920s.]] Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed in a tree. As well as dating them, this can give data for dendroclimatology, the study of climate and atmospheric conditions during different periods in history from the wood of old trees. Dendrochronology derives from the Ancient Greek (), meaning "tree", (), meaning "time", and (), "the study of".

Dendrochronology is useful for determining the precise age of samples, especially those that are too recent for radiocarbon dating, which always produces a range rather than an exact date. However, for a precise date of the death of the tree a full sample to the edge is needed, which most trimmed timber will not provide. It also gives data on the timing of events and rates of change in the environment (most prominently climate) and also in wood found in archaeology or works of art and architecture, such as old panel paintings. It is also used as a check in radiocarbon dating to calibrate radiocarbon ages.