These suffixes can occur in combination on words and most Class I suffixes rarely appear without another suffix on a morphological word. Classes II, III, and IV occur most frequently and are considered the core of syntactic inflection. It is theoretically possible for all sentence suffixes to occur in a sentence, but no case has ever been found. At most three or four sentence suffixes have been found in a text, as of the year 2000. However, because many morphological suffixes can also be stacked, syntactic words frequently carry up to seven or eight suffixes (Hardman, 2000).