1. Current Annual Increment (CAI): It is the increment, which a tree or a crop puts on in a single year.
2. Periodic Annual Increment (PAI): It is the average annual increment for any short period.
3. Total Increment: It is the increment that a tree or a crop puts on from origin upto the age at which the tree or crop is cut. It is sum of all CAIs and therefore represents the volume of the tree or crop.
4. Mean Annual Increment (MAI): It is the total increment upto a given age divided by that age.

CAI and MAI Curves:
When MAI is maximum, the volume production is also maximum and it is when the CAI curve meets the MAI Curve (MAI and CAI culminates).