Descending Chain of Transmission (الإسناد النازل):

This is the opposite of the Ascending Chain of transmission as the number of narrators is more than that found in another chain of transmitters or in the other chains as a whole.

Ascending Chain of Transmission (الإسناد العالي):

This term refers to any hadith whose chain of transmission begins near the Messenger of Allah and the number of narrators is less than that found in another chain of the same hadith or in other chains as a whole.