Plurals

Q. The plural of curriculum is curricula. Why does the dictionary list symposiums as an acceptable plural for symposium? And does the rule differ for every plural of words ending in -um?

A. Curricula is the plural in Latin. In American English, the plural is curriculums. Both are correct, although in academic writing, there is a tradition of using the Latin plurals. Chicago editors follow Merriam-Webster when forming plurals of adopted words, but please see CMOS 7.6.

[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]