In infectious disorders (due to bacteria, viruses etc.) the period between exposure and the development of disease is called incubation period.
It is often measured in days or weeks, and each infectious agent is usually associated with a characteristic incubation period.
Median incubation period: Time required for 50 percent of the cases to occur following exposure.
Latent period: In non-infectious disorders, the period from disease initiation to disease detection.
Intrinsic incubation period: Time period between the entrance of pathogenic organism into a host and the appearance of first symptom of the specific disease.
Intrinsic period helps to estimate the probable date of infection and thereby directs enquiries towards the source of infection.
Extrinsic incubation period: Time period between the entrance of pathogenic organism into a vector or an intermediate host and the maturity of the organism to cause infection in definitive or secondary host.