What is the botanical term for the process that occurs when trees drop their leaves in autumn?

In botany, abscission is the normal separation of a plant part or organ. The purpose is to get rid of a plant part or organ that may no longer be necessary. For instance, leaf abscission is the normal shedding of an old leaf at the base of the petiole such as occurs during autumn. This is believed to be a mechanism of the plant to conserve water or nutrients necessary for growth and photosynthetic potential. It is usually cued by senescence. Plants may also abscise young leaves due to leaf diseases, pest infestation, or damage. This response is a protective mechanism as it decreases the chances of further infestation or damage. Another instance of abscission is fruit drop.