Anagen phase: This is the growing phase of the cycle and can last from three to six years. The hairs in this phase make up about 90% of the hairs on the scalp.

Catagen phase: This is considered to be the breakdown phase of the hair and can last a few weeks.

Telogen phase: This is the dormant or resting phase of the hair that could last many weeks. The follicle continues to shrink during this phase.

This hair cycling is normal and can account for up to 150 hairs lost on a daily basis and these hairs are replaced by the new anagen hairs. The number of hairs on the scalp will stay the same for a person who is not experiencing hair loss.
The duration of each cycle varies for terminal hairs and vellus hairs. Terminal hairs are defined as strong, mature and fully developed hairs. Vellus hair is smaller, miniaturized hair that do not grow longer than a few centimeters and are less pigmented.