The term PLURAL SUFFIX refers to a word ending that is used to indicate that a noun is plural. The two most common examples of this are the suffixes 'ies' and 'ity'. For example, the plural of 'CITY' is 'CITIES' and the plural of 'UNIVERSITY' is 'universities'. Both of these words have the suffix 'ies' added to the end to indicate that they are plural. Similarly, the plural of 'ACTIVITY' is 'activities' and the plural of 'POSSIBILITY' is 'possibilities'. Both of these words have the suffix 'ity' added to the end to indicate that they are plural.