 Roughly speaking, the light suffixes are used with verbs whose subjects are second or third person plural, the third person vowel-initial suffixes are used with verbs that have no agreement suffix, and the heavy suffixes are used in other cases.In the jussive/imperative, the vowel-initial suffixes cause the gemination of the preceding consonant.When an object suffix beginning with a consonant is added to a verb ending in a consonant (either a root or a suffix consonant), a vowel is inserted to break up the cluster, the particular vowel depending on the subject and object.