Acre
An area of land containing 43,560 square feet or 10 square chains. A square acre would be about 209 feet by 209 feet. A circular acre would have a radius of 117.75 feet.

Air Dried
Lumber or other wood products that have been either dried by exposure to natural atmospheric conditions outdoors or in an unheated shed or died to equilibrium with the surrounding atmosphere. Moisture content of air-dried wood fiber depends on relative humidity, temperature, and length of drying period. Also referred to as air seasoned and contracts with kiln dried lumber.

Annual growth rings
The layer of growth that a tree puts on in one year. The annual growth rings can be seen in the end grain of lumber.

Arbor
A shaft, driven by the tool's motor that turns blades or other cutting tools.