The Latin plural is syllabi, and the English plural is syllabuses.
So the plural possessive may be syllabi's or syllabuses' (apostrophe only).
Examples:
The syllabi's exact nature would depend on the professors available for each course.
The dean was in charge of the syllabuses' final forms.
The plural of syllabus is syllabi.
Singular possessive: secretary's Plural: secretaries Plural possessive: secretaries'
The plural form of "syllabus" is "syllabi."
The plural is relatives. The plural possessive is relatives'.
The plural is lads. The plural possessive is lads'.
The plural of syllabus is syllabi.
The plural form of syllabus is syllabior syllabuses.
Singular possessive: secretary's Plural: secretaries Plural possessive: secretaries'
The plural form of "syllabus" is "syllabi."
The plural is relatives. The plural possessive is relatives'.
The plural is lads. The plural possessive is lads'.
The Latin plural is syllabi. But the English plural syllabuses is also used.
The plural form is echoes. The plural possessive is echoes'.
The plural form is suffixes. The plural possessive is suffixes'.
The plural form is Mexicans. The plural possessive is Mexicans'.
The plural form is stepsisters. The plural possessive is stepsisters'.
The plural form is inches. The plural possessive is inches'.