The lifetime of hair is about 4-5 years.
Every man loses daily around 100-150 hair, which is absolutely normal. What should cause concern is the replacement rate.
There is also hair loss of more than 100 daily, of which some do not reappear.
The loss is not steady and shows seasonal fluctuation.
This hair loss is pathological. This way a thinning is crated on the scalp whici according to its size is called alopecia.